Publication by A. Mani Irannejad
Iran: Journal of the British Institute for Persian Studies, 2023
With an origin in western Eurasia, the Indo-Iranian languages appeared in Greater Iran and beyond... more With an origin in western Eurasia, the Indo-Iranian languages appeared in Greater Iran and beyond in the second millennium and were expressed widely in the first millennium BCE. Considering an early separation of Proto-Iranian from the Proto-Indo-Iranian linguistic core, Eurasian archaeological cultures affiliated with Indo-Iranians are revisited. While the Sintashta and Petrovka cultures, along with the Alakul Andronovo cultural complex, are plausible reflections of the Proto-Indo-Aryans, the situation is more complex for the Proto-Iranians who later shaped the cultures of the Scythians and Iranians of Greater Iran. Tracing the origins of these Proto-Iranians in the Inner Asian Mountain Corridor and Central Asia, their possible expansion into Greater Iran, partly separated from the Proto-Indo-Aryan path, is demonstrated. An Iranian speaking group in Transoxiana, distinct from the Iranians of Greater Iran, is also discussed with the Proto-Iranian affiliated Timber Grave culture of western Eurasia as one of its possible components.
Iranian Studies, 2023
While the only surviving legends of Cyrus the Great are found in Graeco-Roman sources, such sourc... more While the only surviving legends of Cyrus the Great are found in Graeco-Roman sources, such sources ultimately speak to the varied views of Cyrus in Achaemenid Iran. Following a survey of the historical conditions leading to the rise of the Persian Empire under Cyrus and its consolidation under Darius, this article explores the characteristics of western Iranian historiography of the Median "state" and dawn of the Persian Empire in the Achaemenid period. This article argues that the Median and Iranian orientation of the Achaemenid Empire from the time of Darius provided the grounds for the infusing of Young Avestan myths and legends in western Iran. In particular, this article investigates parallels between stories of Cyrus the Great and those of Kauui Haosrauuah (Kay Khosrow); an investigation that points to the assimilation of the former with the latter that likely began in the Achaemenid period and later led to a two-way interaction of legends about these figures. In addition, this article also explores the Iranian tradition's depiction of Alexander and his association with Kay Khosrow, which is similar to his association with Cyrus the Great in western sources and may further show Cyrus the Great's assimilation with the Iranian tradition through his identification with Kay Khosrow.
Iran: Journal of the British Institute of Persian Studies, 2022
Zaraθuštra is known as the author of Gāθās and the founder of the ancient Iranian religion. Howev... more Zaraθuštra is known as the author of Gāθās and the founder of the ancient Iranian religion. However, his historicity, time and homeland have been matters of controversy amongst scholars throughout the ages. It is argued that the socio-cultural and archeological evidence in conjunction with available texts enables us to delimit the relatively large time span estimated for the time of the Old Avestan texts from linguistic analysis, which contextualises the Gāθās in the period of Indo-Iranian acculturation of southern Central Asia in the second quarter of the second millennium BCE. Furthermore, the evident social crisis in the Gāθās is seen as a likely reflection of the encroachment of Rig Vedic Proto-Indo-Aryan Andronovo nomads into southern Central Asia and the probable ideological motive for the Old Avestan innovations. In particular, it is argued that the peaceful sedentary lifestyle that the Gāθās envision became the impetus to attract indigenous Greater Iranians and ushered the Iranian acculturation of Greater Iran, leading to the formation of an ancient Iranian Identity, later disseminated into the Iranian plateau.
Persian Journal of Studies of Ancient Iran, 2021
Kavis/Kayanids are amongst the most important building-blocks of the ancient Iranian culture. The... more Kavis/Kayanids are amongst the most important building-blocks of the ancient Iranian culture. The Avestan texts reveal the royal character of Kavis. However, myths of Kauui-Usan/KayUs reveal a Proto-Indo-Iranian inheritance. It is argued that the Avestan texts hint to distinguishing legends of Kauui-Usan/KayUs not to be an integral part of the proper Kayanid dynasty. Also, it is argued that the house of Kauui Vištāspa of the Old Avestan period antedate considerably the proper Kayanid dynasty, which is to be placed in the Young Avestan period. The enumerated traits of the Kayanid dynasty in particular Kauui Haosrauuah in Avestan texts lead to an appreciation of their role in the genesis of Iranian nationality. The historiography evident in the Avestan texts and the place of the Kayanid dynasty in it make it probable that this ideological historiography originated from the Kayanids. In other words, unification of Iranian countries under Kauui Haosrauuah and victory over Turiias were seen as the ultimate encounter of dualism of good and evil mirroring the slaying of Aži Dahāka by Θraētaona. In post-Avestan period, KayUs who was probably the eponym of the Kayanids was diffused into the dynasty. Likewise, the house of kauui Vištāspa was thought of a minor branch of Kayanid dynasty, post-dating the main dynasty and similarly as national Iranian kings. As such, representation of Kavis as a continuous dynasty evident in the Middle Persian and the Perso-Arabic literature is an outcome of evolution of the oral tradition amongst Iranians.
This book seeks to present and detail the worldwide influence of ancient Iranian ideologies and r... more This book seeks to present and detail the worldwide influence of ancient Iranian ideologies and religious practice. It starts from the dawn of Iranian life in pre-history in the realm of mythology and ideology, demonstrating an early Iranian territory in East Iran and Central Asia. Then it steps back to find Indo-European and Indo-Iranian roots and then the expansion of Iranianness from East Iran to the Iranian plateau down to the Achaemenid era. A chapter on various aspects of religion of Zarathustra and Mazdeism provides the influential potency of ancient Iran. Having defined the ethnic, linguistic and religious background, the book proceeds to the early exchange of religious ideas. First, the time of Zarathustra and his whereabouts are introduced. Then, the spread of his vision in Iranian lands is detailed as far as western Iran where it met with other cultures. Arguably, the Iranian religious ideas permeated into the Greek cities of Asia Minor as well as the exiled Jews of Babylon at the dawn of Achaemenid Persian Empire. This phenomenon was the prelude of the widespread flow of Iranian religious ideas and ritual practice into other cultures and civilizations during and after the Achaemenid Persian Empire. By explaining the role of the Achaemenid administration in this process, the Iranian ideology is traced in Persian Period Greek Philosophy and Judaism. In particular, the Iranian ideas, be it from Religion of Zarathustra or Achaemenid ideology, are traced in the post-Achaemenid and intertestamental periods of Judeo-Christian tradition. It is shown that due to the historical process, later Judaism interacted heavily with Iranian ideology by the time of genesis of Christianity. The Iranian impact on Judeo-Christian tradition is detailed in terms of eschatology, angelology, demonology and evolution of monotheism. A brief discussion on Roman Mithraism attempts to find possible Iranian roots of this cult and then its continued existence as assimilated with Christianity. Turning to the east, the Iranian ideological influence on later Hinduism, Buddhism and other eastern traditions are enumerated. Going back to Iran, the ideological dynamics of Sassanian Iran are dealt with. In particular, Manichaeism, Mazdakite movement and the conditions surrounding the formation of national Iranian history are treated. It is attempted to investigate the particulars of Achaemenid memory extant in the national Iranian tradition and their intermingling with Zarathustra’s patron on one side and with the Kayanids on the other side. As an epilogue to Iranian influences on the world of religious ideas, the echoes of Iranian ideology in the Age of Enlightenment are also discussed. In the final chapter, Islam and Iran, the book explores Islamic ideological developments in relation with Iran. The ideological and ritual interactions of early Muslims with other religions, especially Manichaeism is also detailed. A historical section on the Muslim Arab invasion to Iran and its aftermath serves to provide the historical context of Iranian conversion to Islam in the span of six centuries after its rise. The pre-Islamic Iranian heritage facing the conquest brings about the role of Iranians on formation of Islamic culture in terms of its scientific and philosophical movements. As a whole, the book provides a new perspective to the Iranian contribution to the world’s cultural heritage, from the dawn of civilizations to the medieval times, whose impact is still felt in the New Age.
Iranica Antiqua, 2020
The function of kavis and the concept of kāvya have been variously
treated in Iranian studies, gi... more The function of kavis and the concept of kāvya have been variously
treated in Iranian studies, given their diverging paths in Indo-Iranian traditions. The Indo-Iranian myth of kavi seems to be inherited from a Proto-Indo-European “insightful” smith in conjunction with dragon slaying. The special knowledge and thus the wondrous power of fashioning the mace for dragon slaying, termed kāvya, was expanded to include the power of healing shared with the dragon slayer. From the original myth, the Indian tradition highlights the special knowledge, which obtained a verbal attribute; while the smith function and his product, i.e. the metallic weapon are singled out in the Iranian tradition. This latter association presumably led to the adoption of the title of kauui by local chieftains in the Iranian world as early as the Old Avestan period, consequently leading to a dynasty of kauuis, known as Kayāniān or Kayanids. It is argued that this dynasty, postdating the Gāθic kauuis and having the primordial mythical kauui as its eponym, can be historical and the authority behind the first Iranian kingdom in East Iran.
Books by A. Mani Irannejad
ایران و اندیشه های دینی, 2020
This book seeks to present and detail the worldwide influence of ancient Iranian ideologies and r... more This book seeks to present and detail the worldwide influence of ancient Iranian ideologies and religious practice. It starts from the dawn of Iranian life in pre-history in the realm of mythology and ideology, demonstrating an early Iranian territory in East Iran and Central Asia. Then it steps back to find Indo-European and Indo-Iranian roots and then the expansion of Iranianness from East Iran to the Iranian plateau down to the Achaemenid era. A chapter on various aspects of religion of Zarathustra and Mazdeism provides the influential potency of ancient Iran. Having defined the ethnic, linguistic and religious background, the book proceeds to the early exchange of religious ideas. First, the time of Zarathustra and his whereabouts are introduced. Then, the spread of his vision in Iranian lands is detailed as far as western Iran where it met with other cultures. Arguably, the Iranian religious ideas permeated into the Greek cities of Asia Minor as well as the exiled Jews of Babylon at the dawn of Achaemenid Persian Empire. This phenomenon was the prelude of the widespread flow of Iranian religious ideas and ritual practice into other cultures and civilizations during and after the Achaemenid Persian Empire. By explaining the role of the Achaemenid administration in this process, the Iranian ideology is traced in Persian Period Greek Philosophy and Judaism. In particular, the Iranian ideas, be it from Religion of Zarathustra or Achaemenid ideology, are traced in the post-Achaemenid and intertestamental periods of Judeo-Christian tradition. It is shown that due to the historical process, later Judaism interacted heavily with Iranian ideology by the time of genesis of Christianity. The Iranian impact on Judeo-Christian tradition is detailed in terms of eschatology, angelology, demonology and evolution of monotheism. A brief discussion on Roman Mithraism attempts to find possible Iranian roots of this cult and then its continued existence as assimilated with Christianity. Turning to the east, the Iranian ideological influence on later Hinduism, Buddhism and other eastern traditions are enumerated. Going back to Iran, the ideological dynamics of Sassanian Iran are dealt with. In particular, Manichaeism, Mazdakite movement and the conditions surrounding the formation of national Iranian history are treated. It is attempted to investigate the particulars of Achaemenid memory extant in the national Iranian tradition and their intermingling with Zarathustra’s patron on one side and with the Kayanids on the other side. As an epilogue to Iranian influences on the world of religious ideas, the echoes of Iranian ideology in the Age of Enlightenment are also discussed. In the final chapter, Islam and Iran, the book explores Islamic ideological developments in relation with Iran. The ideological and ritual interactions of early Muslims with other religions, especially Manichaeism is also detailed. A historical section on the Muslim Arab invasion to Iran and its aftermath serves to provide the historical context of Iranian conversion to Islam in the span of six centuries after its rise. The pre-Islamic Iranian heritage facing the conquest brings about the role of Iranians on formation of Islamic culture in terms of its scientific and philosophical movements. As a whole, the book provides a new perspective to the Iranian contribution to the world’s cultural heritage, from the dawn of civilizations to the medieval times, whose impact is still felt in the New Age.
Papers by A. Mani Irannejad
A gradient based optimization using the continuous adjoint method for inverse design of a turbine... more A gradient based optimization using the continuous adjoint method for inverse design of a turbine blade cascade is presented. The advantage of the adjoint method is that the objective function gradients can be evaluated by solving the adjoint equations with coefficients depending on the flow variables. This method is particularly suitable for aerodynamic design optimization for which the number of design variables is large. Bezier polynomials are used to parameterize suction side of the turbine blade. The numerical convective fluxes of both flow and adjoint equations are computed by using a Roe-type approximate Riemann solver. An approximate linearization is applied to simplify the calculation of the numerical flux of adjoint variables on the faces of computational cell. The problem examined is that of the inverse design of NASA C3X blade that reproduces a given pressure distributions over its surfaces. Adjoint results show a good agreement with those obtained by finite-difference method.
n this paper, the effect of turbine stage efficiency on fuel consumption of both gas turbines and... more n this paper, the effect of turbine stage efficiency on fuel consumption of both gas turbines and aerial engines is assessed quantitatively. At the beginning of the gas generator optimization to decrease the fuel consumption, it is necessary to analyze the sensitivity of fuel consumption to its main components efficiencies. This will guide us which component is more important to be optimized. Here a zero-dimensional analysis has been done to determine the effect of turbine stage efficiency on the fuel consumption. Results of this analysis are evaluated in the context of thermodynamic cycle of a gas turbine generator and an aerial engine. As an example, it is shown that if the efficiency of first stage of the turbine is increased from 82% to 84%, the fuel consumption of an aerial engine is computed to be decreased by 1%. The cycle analysis performed implies that the sensitivity of fuel consumption to turbine stage efficiency varies for different values of stage efficiency.
The two-phase filtered mass density function (FMDF) method is employed for large eddy simulation ... more The two-phase filtered mass density function (FMDF) method is employed for large eddy simulation (LES) of high speed evaporating and combusting n-heptane sprays using simple (global) and complex (skeletal) chemical kinetic mechanisms. The resolved fluid velocity and pressure fields are obtained by solving the filtered compressible Navier–Stokes equations with high-order Eulerian finite difference methods. The liquid spray and gas scalar (temperature and species mass fractions) fields are both obtained by Lagrangian stochastic models. The chemistry calculation is accelerated by incorporating the parallel in situ adaptive tabulation (ISAT) method. There are two-way interactions among Eulerian and Lagrangian fields. Simulations of evaporating sprays with and without combustion indicate that the two-phase LES/FMDF results are consistent and compare well with the available experimental data at different gas temperatures and oxygen concentrations. The spray controlled flame tends to move away from a diffusion flame structure toward a premixed one as the oxygen concentration decreases and/or the ambient gas temperature increases because of changes in spray-induced turbulence and mixing. The LES/FMDF results for ignition delay show more sensitivity to the chemical kinetic model at lower gas temperatures due to slower reaction and stronger turbulence–chemistry interactions. The liftoff length is less sensitive to the kinetics.
Large eddy simulations of high speed evaporating sprays are conducted to study spray interactions... more Large eddy simulations of high speed evaporating sprays are conducted to study spray interactions with the gas flow and turbulence generated by the spray. The spray is simulated with a Lagrangian droplet method and a stochastic breakup model together with non-equilibrium, finite-rate heat and mass transfer models. The Lagrangian spray/droplet field is fully coupled with the Eulerian gas flow through mass, momentum and energy coupling terms. The interaction of spray induced gas flow and turbulence with the droplets is studied for different gas chamber densities and temperatures as well as different nozzle sizes and injection pressures. Our results indicate that although the droplet transport and evaporation are both important to the generated gas flow and its interactions with the spray, the major source of momentum transfer to the gas is the high speed vapor generated by evaporation. It is shown that sprays injected from larger nozzles generate more perturbations in the gas due to increase in evaporation rate by higher entrained gas. However, the liquid spray penetration remains unchanged with the variation in injection pressure due to competing effects of evaporation and vapor convection. While the liquid penetration is not significantly affected by the injection pressure, the evaporated vapor penetrates more and mixes better at higher injection pressures due to higher induced gas velocity and turbulence.
In this work, the filtered mass density function (FMDF) methodology is implemented in the discont... more In this work, the filtered mass density function (FMDF) methodology is implemented in the discontinuous spectral element method (DSEM) for simulation of reacting flows in complex geometries. DSEM solves the compressible Navier-Stokes equations on an unstructured grid with high orders of accuracy. The FMDF is a probability density function method that has been developed for large eddy simulation (LES) of variable-density chemically reacting turbulent flows. The solution to the modeled FMDF transport equation is obtained by solving an equivalent set of stochastic differential equations (SDEs) which yield statistically equivalent results. The set of SDEs is solved by means of a Lagrangian Monte Carlo scheme. The validity of the scalar FMDF is appraised by determining the consistency against DSEM in a temporally developing shear layer. Additional results are shown for the DSEM-LES/FMDF simulation of a hydrogen-air reaction in a temporally-developing shear layer.
Bulletin of the American Physical Society, 2019
he filtered mass density function (FMDF) methodology is further extended and employed for large-e... more he filtered mass density function (FMDF) methodology is further extended and employed for large-eddy simulations (LES) of multiphase turbulent reacting flows. The two-phase LES/FMDF model is implemented with a unique Lagrangian-Eulerian-Lagrangian mathematical/computational methodology. In this methodology, the filtered carrier gas velocity field is obtained by solving the filtered form of the compressible Navier-Stokes equations while the gas scalar (e.g. temperature and species mass fractions) field and the liquid (spray) phase are obtained by solving two different sets of Lagrangian equations. The two-way interactions between the phases and all the Eulerian and Lagrangian fields are included in the two-phase LES/FMDF methodology. The accuracy and reliability of the model is demonstrated by comparing the two-phase LES/FMDF results with those obtained from the direct numerical simulation (DNS) and experimental data for a range of fundamental and practical multiphase flows including a spatially developing turbulent mixing layer with evaporating and reacting droplets and spray combustion in a preheated high-pressure closed chamber, a dump combustor, a double-swirl burner, and an internal combustion engine.
Conference Presentations by A. Mani Irannejad
A high–fidelity two-phase large eddy simulation
(LES)/filtered mass density function (FMDF) mode... more A high–fidelity two-phase large eddy simulation
(LES)/filtered mass density function (FMDF) model is
developed and used for detailed simulations of turbulent spray
breakup, evaporation and combustion. The spray is simulated
with Lagrangian droplet transport, stochastic breakup, wake,
collision/coalescence and finite rate heat and mass transfer
submodels. The spray model is used together with the
compressible, Eulerian LES gas flow model for velocity and
pressure fields and the two-phase Lagrangian FMDF for the
scalar (species mass fraction and enthalpy) field. There are
two-way couplings between all Lagrangian and Eulerian
models. The numerical results for non-reacting and reacting
sprays are compared with the available experimental data for
global spray variables such as the spray penetration length,
ignition delay and flame lift-off lengths. It is shown that the
two-phase LES/FMDF results are consistent and compare well
with the experimental data.
In this work, the filtered mass density function (FMDF) methodology is implemented in the discont... more In this work, the filtered mass density function (FMDF) methodology is implemented in the discontinuous spectral element method (DSEM) for simulation of reacting flows in complex geometries. DSEM solves the compressible Navier-Stokes equations on an unstructured grid with high orders of accuracy. The FMDF is a probability density function method that has been developed for large eddy simulation (LES) of variable-density chemically reacting turbulent flows. The solution to the modeled FMDF transport equation is obtained by solving an equivalent set of stochastic differential equations (SDEs) which yield statistically equivalent results. The set of SDEs is solved by means of a Lagrangian Monte Carlo scheme. The validity of the scalar FMDF is appraised by determining the consistency against DSEM in a temporally developing shear layer. Additional results are shown for the DSEM-LES/FMDF simulation of a hydrogen-air reaction in a temporally-developing shear layer.
Uploads
Publication by A. Mani Irannejad
treated in Iranian studies, given their diverging paths in Indo-Iranian traditions. The Indo-Iranian myth of kavi seems to be inherited from a Proto-Indo-European “insightful” smith in conjunction with dragon slaying. The special knowledge and thus the wondrous power of fashioning the mace for dragon slaying, termed kāvya, was expanded to include the power of healing shared with the dragon slayer. From the original myth, the Indian tradition highlights the special knowledge, which obtained a verbal attribute; while the smith function and his product, i.e. the metallic weapon are singled out in the Iranian tradition. This latter association presumably led to the adoption of the title of kauui by local chieftains in the Iranian world as early as the Old Avestan period, consequently leading to a dynasty of kauuis, known as Kayāniān or Kayanids. It is argued that this dynasty, postdating the Gāθic kauuis and having the primordial mythical kauui as its eponym, can be historical and the authority behind the first Iranian kingdom in East Iran.
Books by A. Mani Irannejad
Papers by A. Mani Irannejad
Conference Presentations by A. Mani Irannejad
(LES)/filtered mass density function (FMDF) model is
developed and used for detailed simulations of turbulent spray
breakup, evaporation and combustion. The spray is simulated
with Lagrangian droplet transport, stochastic breakup, wake,
collision/coalescence and finite rate heat and mass transfer
submodels. The spray model is used together with the
compressible, Eulerian LES gas flow model for velocity and
pressure fields and the two-phase Lagrangian FMDF for the
scalar (species mass fraction and enthalpy) field. There are
two-way couplings between all Lagrangian and Eulerian
models. The numerical results for non-reacting and reacting
sprays are compared with the available experimental data for
global spray variables such as the spray penetration length,
ignition delay and flame lift-off lengths. It is shown that the
two-phase LES/FMDF results are consistent and compare well
with the experimental data.
treated in Iranian studies, given their diverging paths in Indo-Iranian traditions. The Indo-Iranian myth of kavi seems to be inherited from a Proto-Indo-European “insightful” smith in conjunction with dragon slaying. The special knowledge and thus the wondrous power of fashioning the mace for dragon slaying, termed kāvya, was expanded to include the power of healing shared with the dragon slayer. From the original myth, the Indian tradition highlights the special knowledge, which obtained a verbal attribute; while the smith function and his product, i.e. the metallic weapon are singled out in the Iranian tradition. This latter association presumably led to the adoption of the title of kauui by local chieftains in the Iranian world as early as the Old Avestan period, consequently leading to a dynasty of kauuis, known as Kayāniān or Kayanids. It is argued that this dynasty, postdating the Gāθic kauuis and having the primordial mythical kauui as its eponym, can be historical and the authority behind the first Iranian kingdom in East Iran.
(LES)/filtered mass density function (FMDF) model is
developed and used for detailed simulations of turbulent spray
breakup, evaporation and combustion. The spray is simulated
with Lagrangian droplet transport, stochastic breakup, wake,
collision/coalescence and finite rate heat and mass transfer
submodels. The spray model is used together with the
compressible, Eulerian LES gas flow model for velocity and
pressure fields and the two-phase Lagrangian FMDF for the
scalar (species mass fraction and enthalpy) field. There are
two-way couplings between all Lagrangian and Eulerian
models. The numerical results for non-reacting and reacting
sprays are compared with the available experimental data for
global spray variables such as the spray penetration length,
ignition delay and flame lift-off lengths. It is shown that the
two-phase LES/FMDF results are consistent and compare well
with the experimental data.
To use computational fluid dynamics to evaluate the intraoperative flow performance of dual-cutting 20,000 cpm probes and single-cutting 10,000 cpm probes.
Setting/Venue:
Computer simulation of vitrectomy. Comparison of flow behavior of two different 27-gauge vitrectomy probe designs
Methods:
The 27+® HyperVit® dual-cutting 20,000 cpm probe with a flat tip was modelled and compared to the computational model of a 27+® Advanced UltraVit® single-cutting 10,000 cpm probe with a beveled tip. A dynamic mesh was used to simulate the motion of the cutter. The fluid in the clearance between the cutter and the needle was taken into account. With the CONSTELLATION® Vision System, the following system parameters were incorporated into the simulation: applied vacuum settings of 200, 400, and 650 mmHg, 30 mmHg IOP, and 50/50 duty cycle for one complete cut cycle. Simulations were generated for a liquid water environment and also a viscous fluid environment to represent vitreous. Flow was assumed to be incompressible and laminar. In this study, overall mass flow rates and applied pressure on the retina was evaluated.
Results:
Flow behavior of the two different fluid models was significantly different. This was the result of the change in balance of inertial forces of the liquid flow compared to viscous forces due to the transient nature of the flow. The dual-cutting/flat-tipped 20,000 cpm probe generated higher mass flow rates than the single-cutting/beveled-tip 10,000 cpm probes. A dead fluid zone was identified and resulted in back flow or retropulsion. The beveled shape of the 10,000 cpm probes contributed to reduced back flow. Less back flow or retropulsion was associated with the 20,000 cpm dual-cutting probes compared to single-cutting 10,000 cpm beveled-tip probes. Pressure on the retina fluctuated during the cut cycle. At equivalent vacuum settings, dual-cutting probes generated higher applied pressure to the retina than single-cutting probes.
Conclusions:
Simulated results showed the expected improvement of mass flow rate for dual-cutting 20,000 cpm probes compared to single-cutting 10,000 cpm probes. The impact of a beveled tip design on back flow was also revealed. Dual-cutting 20,000 cpm probes resulted in less back flow/less retropulsion and improved intraoperative flow stability. Simulations may help surgeons better understand differences in probe performance and help identify necessary adjustments to surgical settings.
During vitrectomy, the dynamics of probe aspiration is complex. The use of modeling and simulation to analyze fluid during vitrectomy may help improve the design of current cutters and help surgeons better understand performance of new vitrectomy probes. This study evaluated the fluid dynamics of balanced salt solution during vitrectomy of 27 gauge dual-cutting 20,000 cpm probes and single-cutting 10,000 cpm probes.
Setting/Venue:
Computer simulation of vitrectomy. Comparison of velocity characteristics associated with different 27-gauge vitrectomy probe designs.
Methods:
Vitrectomy aspiration of two different probes were modelled: 1) 27+® HyperVit® dual-cutting 20,000 cpm probes with a flat tip and 2) 27+® Advanced UltraVit® single-cutting 10,000 cpm probes with a beveled tip. Motion of the cutter in the needle was simulated using a dynamic mesh that took into account the fluid in the clearance between the cutter and the needle. Flare and bend of the inner cutter was not taken into account. Vitrectomy system parameters such as applied vacuum settings of 200, 400, and 650 mmHg, an IOP setting of 30 mmHg, and 50/50 duty cycle setting on the CONSTELLATION® Vision System were simulated in balanced salt solution. For each probe, evaluations included comparisons of velocity streamlines, vector fields, and sphere of influence. The simulation duration covered one cut cycle of the cutter.
Results:
When comparing probes, the velocity streamlines revealed behavioral differences inside the cutter: Dual-cutting 20,000 cpm probes demonstrated less internal transience than single-cutting 10,000cpm probes. External velocity streamlines showed differences in fluid behavior outside of the cutter at different time points during the cut cycle. Vector field images visually showed differences in near field fluid behavior between both cutter designs. Lower vacuum settings resulted in a smaller sphere of influence.
Conclusions:
Computer simulations of velocity streamlines and vector fields revealed differences in both internal and external fluid behavior. Additional velocity analysis showed how system parameters affect the sphere of influence for a particular probe design. Simulations may help surgeons better understand the performance of new cutters and ultimately, optimize system settings and intraoperative surgical techniques.
The purpose of this study is to evaluate the impact of probe tip design on aspiration performance.
Setting: 50 words max
Computer modeling and simulation
Methods: 125/200 words max
Two different 25+® Advanced UltraVit 10,000 cuts per minute probe tip designs were modelled and compared: 1) beveled tip and 2) flat tip. A dynamic mesh was used to simulate the motion of the cutter. Vitrectomy system parameters such as applied vacuum settings of 650 mmHg, an IOP setting of 30 mmHg, and 50/50 duty cycle setting on the CONSTELLATION® Vision System were simulated. A viscous Newtonian fluid environment was used to represent vitreous. Flow was assumed to be incompressible and laminar. The simulation was performed and the results were extracted for one cut cycle after the cyclic flow was established. Root Mean Square (RMS) was used to evaluate the intensity of pulsatile motion at various distances from the probe port (1-3 mm at 0.5 mm intervals). All products are made by Alcon, Fort Worth, TX.
Results: 113/200 words max
At a location of 1 mm away from the port, the beveled design resulted in a 6% reduction in the intensity of velocity fluctuations compared to the flat design. The mean velocity was 35% lower for the beveled tip at 1 mm from the probe tip compared to the flat tip. Both beveled and flat tip probes resulted in a 87% reduction in RMS intensity at distances further from the probe port. The beveled tip RMS intensity reduced from 0.56 at 1 mm from the port to 0.08 at 3 mm from the port. Similarly, the flat tip reduced from 0.60 at 1 mm from the port to 0.07 at 3 mm from the port.
Conclusion: 59/200 words max
The simulated flow performance of the 25-gauge beveled tip probe design showed a reduction in the pulse intensity of velocity during viscous fluid aspiration. In other words, the beveled tip design contributed to reduced pulsatile motion or more stable aspiration than the flat tip design. Simulations may help surgeons better understand differences in probe performance and optimize instrument selection.