3D bioprinting has begun to show great promise in advancing the development of functional tissue/... more 3D bioprinting has begun to show great promise in advancing the development of functional tissue/organ replacements. However, to realize the true potential of 3D bioprinted tissues for clinical use requires the fabrication of an interconnected and effective vascular network. Solving this challenge is critical, as human tissue relies on an adequate network of blood vessels to transport oxygen, nutrients, other chemicals, biological factors and waste, in and out of the tissue. Here, we have successfully designed and printed a series of novel 3D bone scaffolds with both bone formation supporting structures and highly interconnected 3D microvascular mimicking channels, for efficient and enhanced osteogenic bone regeneration as well as vascular cell growth. Using a chemical functionalization process, we have conjugated our samples with nano hydroxyapatite (nHA), for the creation of novel micro and nano featured devices for vascularized bone growth. We evaluated our scaffolds with mechani...
The cabin air ventilation system in wide body jetliners is designed to provide a comfortable and ... more The cabin air ventilation system in wide body jetliners is designed to provide a comfortable and controlled environment for passengers. Inside the cabin, the air flows continuously from overhead vents into sidewall exhausts, forming a circular pattern designed to minimize cross flow between adjacent seat rows. However, spreading of gaseous or particulate contaminants is possible when flight attendants or passengers walk along an aisle, perturbing the ventilation flow. Such unsteady flow perturbations have been found to alter the cabin air distribution and quality. A better fundamental understanding of the turbulent transport phenomena is needed to improve air quality monitoring and control systems and to validate numerical simulations. The velocity field in a 15:1 model of a simplified aircraft cabin is probed to investigate the wake of a rectangular body moving through a steady two-dimensional flow at a Reynolds number (based on body height) of the order of 50,000. Planar Laser Ind...
ABSTRACT Secondary flow vortical patterns in arterial curvatures have the potential to affect sev... more ABSTRACT Secondary flow vortical patterns in arterial curvatures have the potential to affect several cardiovascular phenomena, e. g., progression of atherosclerosis by altering wall shear stresses, carotid atheromatous disease, thoracic aortic aneurysms and Marfan's syndrome. Temporal characteristics of secondary flow structures vis-a-vis physiological (pulsatile) inflow waveform were explored by continuous wavelet transform (CWT) analysis of phase-locked, two-component, two-dimensional particle image velocimeter data. Measurements were made in a 180 degrees curved artery test section upstream of the curvature and at the 90 degrees cross-sectional plane. Streamwise, upstream flow rate measurements were analyzed using a one-dimensional antisymmetric wavelet. Cross-stream measurements at the 90 degrees location of the curved artery revealed interesting multi-scale, multi-strength coherent secondary flow structures. An automated process for coherent structure detection and vortical feature quantification was applied to large ensembles of PIV data. Metrics such as the number of secondary flow structures, their sizes and strengths were generated at every discrete time instance of the physiological inflow waveform. An autonomous data post-processing method incorporating two-dimensional CWT for coherent structure detection was implemented. Loss of coherence in secondary flow structures during the systolic deceleration phase is observed in accordance with previous research. The algorithmic approach presented herein further elucidated the sensitivity and dependence of morphological changes in secondary flow structures on quasiperiodicity and magnitude of temporal gradients in physiological inflow conditions.
An indeterminate-origin (IO) nozzle consisting of a four-point tapered crown geometry is used to ... more An indeterminate-origin (IO) nozzle consisting of a four-point tapered crown geometry is used to control jet structure and evolution. The near-field structure and flow field of round water jets were studied with particle image velocimetry (PIV) and laser-induced fluorescence (LIF) techniques. Typical jet Reynolds numbers (based on the nozzle diameter) are 5 000–10 000. The jet structures for IO nozzles
An experimental research program was undertaken to examine the influence of large-scale high-inte... more An experimental research program was undertaken to examine the influence of large-scale high-intensity turbulence on vane exit losses, wake growth, and exit turbulence characteristics. The experiment was conducted in a four-vane linear cascade at an exit Reynolds number of 800,000 based on chord length and an exit Mach number of 0.27. Exit measurements were made for four inlet turbulence conditions
Page 1. www.coatingstech.org Transfer Efficiency for Airless Painting Systems Michael W. Plesniak... more Page 1. www.coatingstech.org Transfer Efficiency for Airless Painting Systems Michael W. Plesniak, Paul E. Sojka, and Anshul K. SinghPurdue University* *Maurice J. Zucrow Laboratories, School of Mechanical Engineering, West Lafayette, IN 47907-1003. ...
Aps Division of Fluid Dynamics Meeting Abstracts, Nov 1, 2010
Secondary flow structures were investigated in a 180-degree circular bend under physiological (pu... more Secondary flow structures were investigated in a 180-degree circular bend under physiological (pulsatile) flow conditions with a stent model installed upstream of the bend. Upstream Reynolds number ranged from 200 to 1400 and the cardiac cycle period was scaled to match the physiological Womersley number, Wo=4.2. Experimental data were acquired using 2-D PIV at various cross-sectional planes along the bend. Similar to the results in absence of the stent model, symmetric counter-rotating vortex pairs were observed to develop during the cardiac cycle. In addition, transient unstable flow was initiated at the deceleration phase of the systolic peak (t/T=0.21). This complex flow is mainly attributable to perturbations induced by the stent model. It is characterized by breakdown of Dean- and Lyne-type vortices into various multiple-scale vortices. The phase-averaged flow fields were analyzed using the proper orthogonal decomposition (POD) method to gain further insight regarding the structural features of the flow.
Under forced harmonic oscillation at sufficiently high Womersley number, the secondary flow patte... more Under forced harmonic oscillation at sufficiently high Womersley number, the secondary flow pattern in a tube can exhibit Lyne-type vortices, where an inviscid core in the center of the tube experiences inward centrifuging. The present study investigates the evolution of secondary flow development in a curved tube subjected to a physiologically-inspired pulsatile waveform constructed using 10 harmonics. Specifically, the study seeks to address whether a Lyne-type effect is possible at a nominally low Womersley number. Experimental data were acquired using Laser Doppler Velocimetry (LDV) and numerical simulations were conducted using Fluent. Experimental and numerical results show fully developed flow after approximately 150 degrees for all phases of the driving waveform. This is in agreement with previous studies of harmonic forcing. For the lower Reynolds number portions of the waveform, flow development can occur as early as 135 degrees according to experimental data. Lyne-type vortices were observed at portions of the waveform dominated by higher harmonics, such as the peak associated with systole.
Bulletin of the American Physical Society, Nov 1, 2008
Human speech is made possible by the air flow interaction with the vocal folds. During phonation,... more Human speech is made possible by the air flow interaction with the vocal folds. During phonation, asymmetries in the glottal flow field may arise from flow phenomena (e.g. the Coanda effect) as well as from pathological vocal fold motion (e.g. unilateral paralysis). In this study, the effects of flow asymmetries on glottal sound sources were investigated. Dynamically-programmable 7.5 times life-size vocal fold models with 2 degrees-of-freedom (linear and rotational) were constructed to provide a first-order approximation of vocal fold motion. Important parameters (Reynolds, Strouhal, and Euler numbers) were scaled to physiological values. Normal and abnormal vocal fold motions were synthesized, and the velocity field and instantaneous transglottal pressure drop were measured. Variability in the glottal jet trajectory necessitated sorting of the data according to the resulting flow configuration. The dipole sound source is related to the transglottal pressure drop via acoustic analogies. Variations in the transglottal pressure drop (and subsequently the dipole sound source) arising from flow asymmetries are discussed.
Inward centrifuging of fluid in a 180 degree curved pipe leads to development of secondary flow v... more Inward centrifuging of fluid in a 180 degree curved pipe leads to development of secondary flow vortical structures. These Dean's vortices have been widely studied in steady flows. Complex secondary flow structures were observed under (unsteady) physiological flow forcing ...
An experimental study was conducted concerning the influence of small changes in initial conditio... more An experimental study was conducted concerning the influence of small changes in initial conditions on the near- and far-field evolution of the three-dimensional structure of a plan mixing layer. A two-stream mixing layer with a velocity ratio of 0.6 was generated with the initial boundary layers on the splitter plate laminar and was nominally two-dimensional. The initial conditions were changed slightly by interchanging the high- and low-speed sides of the wind tunnel, while maintaining the same velocities, and hence velocity ratio. This resulted in small changes in the initial boundary layer properties, and the perturbations present in the boundary layers were interchanged between the high- and low-speed sides for the two cases. The results indicate that, even with this relatively minor change in initial conditions, the near-field regions of the two cases differ significantly. The peak Reynolds stress levels in the near-field differ by up to 100 percent, and this is attributed to a difference in the location of the initial spanwise vortex roll-up. In addition, the positions and shapes of the individual streamwise vortical structures differ for the two cases, although the overall structures differ for the two cases, although the overall qualitative description of these structures is comparable. The subsequent reorganization and decay of the streamwise vortical structures is very similar for the two cases. As a result, in the far field, both mixing layers achieve similar structure, yielding comparable growth rates, Reynolds stress, distribution, and spectral content.
Aps Division of Fluid Dynamics Meeting Abstracts, 2003
Human speech is initiated as air passing through the glottis triggers self-sustained oscillations... more Human speech is initiated as air passing through the glottis triggers self-sustained oscillations of the vocal folds. These oscillations, caused by aerodynamic air pressures, glottal geometry and tissue properties, result in the glottis cyclically forming into a converging, straight, then diverging passage and finally closing. The varying shape of the glottis throughout the cycle causes different coherent structures to form. One such phenomenon evident in quasi-steady flow experiments is the skewing of the glottal jet towards one wall and attachment, i.e. the Coanda effect. It is not understood if the high frequency oscillations inherent in human phonation allow sufficient time for this oscillating jet to attach to the glottal wall, and thereby influence sound production. Unsteady flow through a high aspect ratio slot with an adjacent plate angled at 30 degrees to the streamwise direction was investigated. The driven, unsteady flow oscillation through the slot was chosen to represent known in-vivo velocity wave forms. Particle Image Velocimetry (PIV) was used to measure the phase-averaged development of the Coanda effect. The evolution of the unsteady Coanda effect over a range of frequencies typical of human phonation will be discussed.
Secondary flow structures were investigated in a 180-degree circular bend under physiological (pu... more Secondary flow structures were investigated in a 180-degree circular bend under physiological (pulsatile) flow conditions with a stent model installed upstream of the bend. Upstream Reynolds number ranged from 200 to 1400 and the cardiac cycle period was scaled to match the physiological Womersley number, Wo=4.2. Experimental data were acquired using 2-D PIV at various cross-sectional planes along the bend. Similar to the results in absence of the stent model, symmetric counter-rotating vortex pairs were observed to develop during the cardiac cycle. In addition, transient unstable flow was initiated at the deceleration phase of the systolic peak (t/T=0.21). This complex flow is mainly attributable to perturbations induced by the stent model. It is characterized by breakdown of Dean- and Lyne-type vortices into various multiple-scale vortices. The phase-averaged flow fields were analyzed using the proper orthogonal decomposition (POD) method to gain further insight regarding the stru...
43rd AIAA Aerospace Sciences Meeting and Exhibit, 2005
Large eddy simulations (LES) of low-speed, wall-bounded turbulent flows were conducted by numeric... more Large eddy simulations (LES) of low-speed, wall-bounded turbulent flows were conducted by numerically integrating the compressible Navier-Stokes equations in a generalized curvilinear coordinate system. An efficient numerical scheme based on a third-order ...
3D bioprinting has begun to show great promise in advancing the development of functional tissue/... more 3D bioprinting has begun to show great promise in advancing the development of functional tissue/organ replacements. However, to realize the true potential of 3D bioprinted tissues for clinical use requires the fabrication of an interconnected and effective vascular network. Solving this challenge is critical, as human tissue relies on an adequate network of blood vessels to transport oxygen, nutrients, other chemicals, biological factors and waste, in and out of the tissue. Here, we have successfully designed and printed a series of novel 3D bone scaffolds with both bone formation supporting structures and highly interconnected 3D microvascular mimicking channels, for efficient and enhanced osteogenic bone regeneration as well as vascular cell growth. Using a chemical functionalization process, we have conjugated our samples with nano hydroxyapatite (nHA), for the creation of novel micro and nano featured devices for vascularized bone growth. We evaluated our scaffolds with mechani...
The cabin air ventilation system in wide body jetliners is designed to provide a comfortable and ... more The cabin air ventilation system in wide body jetliners is designed to provide a comfortable and controlled environment for passengers. Inside the cabin, the air flows continuously from overhead vents into sidewall exhausts, forming a circular pattern designed to minimize cross flow between adjacent seat rows. However, spreading of gaseous or particulate contaminants is possible when flight attendants or passengers walk along an aisle, perturbing the ventilation flow. Such unsteady flow perturbations have been found to alter the cabin air distribution and quality. A better fundamental understanding of the turbulent transport phenomena is needed to improve air quality monitoring and control systems and to validate numerical simulations. The velocity field in a 15:1 model of a simplified aircraft cabin is probed to investigate the wake of a rectangular body moving through a steady two-dimensional flow at a Reynolds number (based on body height) of the order of 50,000. Planar Laser Ind...
ABSTRACT Secondary flow vortical patterns in arterial curvatures have the potential to affect sev... more ABSTRACT Secondary flow vortical patterns in arterial curvatures have the potential to affect several cardiovascular phenomena, e. g., progression of atherosclerosis by altering wall shear stresses, carotid atheromatous disease, thoracic aortic aneurysms and Marfan's syndrome. Temporal characteristics of secondary flow structures vis-a-vis physiological (pulsatile) inflow waveform were explored by continuous wavelet transform (CWT) analysis of phase-locked, two-component, two-dimensional particle image velocimeter data. Measurements were made in a 180 degrees curved artery test section upstream of the curvature and at the 90 degrees cross-sectional plane. Streamwise, upstream flow rate measurements were analyzed using a one-dimensional antisymmetric wavelet. Cross-stream measurements at the 90 degrees location of the curved artery revealed interesting multi-scale, multi-strength coherent secondary flow structures. An automated process for coherent structure detection and vortical feature quantification was applied to large ensembles of PIV data. Metrics such as the number of secondary flow structures, their sizes and strengths were generated at every discrete time instance of the physiological inflow waveform. An autonomous data post-processing method incorporating two-dimensional CWT for coherent structure detection was implemented. Loss of coherence in secondary flow structures during the systolic deceleration phase is observed in accordance with previous research. The algorithmic approach presented herein further elucidated the sensitivity and dependence of morphological changes in secondary flow structures on quasiperiodicity and magnitude of temporal gradients in physiological inflow conditions.
An indeterminate-origin (IO) nozzle consisting of a four-point tapered crown geometry is used to ... more An indeterminate-origin (IO) nozzle consisting of a four-point tapered crown geometry is used to control jet structure and evolution. The near-field structure and flow field of round water jets were studied with particle image velocimetry (PIV) and laser-induced fluorescence (LIF) techniques. Typical jet Reynolds numbers (based on the nozzle diameter) are 5 000–10 000. The jet structures for IO nozzles
An experimental research program was undertaken to examine the influence of large-scale high-inte... more An experimental research program was undertaken to examine the influence of large-scale high-intensity turbulence on vane exit losses, wake growth, and exit turbulence characteristics. The experiment was conducted in a four-vane linear cascade at an exit Reynolds number of 800,000 based on chord length and an exit Mach number of 0.27. Exit measurements were made for four inlet turbulence conditions
Page 1. www.coatingstech.org Transfer Efficiency for Airless Painting Systems Michael W. Plesniak... more Page 1. www.coatingstech.org Transfer Efficiency for Airless Painting Systems Michael W. Plesniak, Paul E. Sojka, and Anshul K. SinghPurdue University* *Maurice J. Zucrow Laboratories, School of Mechanical Engineering, West Lafayette, IN 47907-1003. ...
Aps Division of Fluid Dynamics Meeting Abstracts, Nov 1, 2010
Secondary flow structures were investigated in a 180-degree circular bend under physiological (pu... more Secondary flow structures were investigated in a 180-degree circular bend under physiological (pulsatile) flow conditions with a stent model installed upstream of the bend. Upstream Reynolds number ranged from 200 to 1400 and the cardiac cycle period was scaled to match the physiological Womersley number, Wo=4.2. Experimental data were acquired using 2-D PIV at various cross-sectional planes along the bend. Similar to the results in absence of the stent model, symmetric counter-rotating vortex pairs were observed to develop during the cardiac cycle. In addition, transient unstable flow was initiated at the deceleration phase of the systolic peak (t/T=0.21). This complex flow is mainly attributable to perturbations induced by the stent model. It is characterized by breakdown of Dean- and Lyne-type vortices into various multiple-scale vortices. The phase-averaged flow fields were analyzed using the proper orthogonal decomposition (POD) method to gain further insight regarding the structural features of the flow.
Under forced harmonic oscillation at sufficiently high Womersley number, the secondary flow patte... more Under forced harmonic oscillation at sufficiently high Womersley number, the secondary flow pattern in a tube can exhibit Lyne-type vortices, where an inviscid core in the center of the tube experiences inward centrifuging. The present study investigates the evolution of secondary flow development in a curved tube subjected to a physiologically-inspired pulsatile waveform constructed using 10 harmonics. Specifically, the study seeks to address whether a Lyne-type effect is possible at a nominally low Womersley number. Experimental data were acquired using Laser Doppler Velocimetry (LDV) and numerical simulations were conducted using Fluent. Experimental and numerical results show fully developed flow after approximately 150 degrees for all phases of the driving waveform. This is in agreement with previous studies of harmonic forcing. For the lower Reynolds number portions of the waveform, flow development can occur as early as 135 degrees according to experimental data. Lyne-type vortices were observed at portions of the waveform dominated by higher harmonics, such as the peak associated with systole.
Bulletin of the American Physical Society, Nov 1, 2008
Human speech is made possible by the air flow interaction with the vocal folds. During phonation,... more Human speech is made possible by the air flow interaction with the vocal folds. During phonation, asymmetries in the glottal flow field may arise from flow phenomena (e.g. the Coanda effect) as well as from pathological vocal fold motion (e.g. unilateral paralysis). In this study, the effects of flow asymmetries on glottal sound sources were investigated. Dynamically-programmable 7.5 times life-size vocal fold models with 2 degrees-of-freedom (linear and rotational) were constructed to provide a first-order approximation of vocal fold motion. Important parameters (Reynolds, Strouhal, and Euler numbers) were scaled to physiological values. Normal and abnormal vocal fold motions were synthesized, and the velocity field and instantaneous transglottal pressure drop were measured. Variability in the glottal jet trajectory necessitated sorting of the data according to the resulting flow configuration. The dipole sound source is related to the transglottal pressure drop via acoustic analogies. Variations in the transglottal pressure drop (and subsequently the dipole sound source) arising from flow asymmetries are discussed.
Inward centrifuging of fluid in a 180 degree curved pipe leads to development of secondary flow v... more Inward centrifuging of fluid in a 180 degree curved pipe leads to development of secondary flow vortical structures. These Dean's vortices have been widely studied in steady flows. Complex secondary flow structures were observed under (unsteady) physiological flow forcing ...
An experimental study was conducted concerning the influence of small changes in initial conditio... more An experimental study was conducted concerning the influence of small changes in initial conditions on the near- and far-field evolution of the three-dimensional structure of a plan mixing layer. A two-stream mixing layer with a velocity ratio of 0.6 was generated with the initial boundary layers on the splitter plate laminar and was nominally two-dimensional. The initial conditions were changed slightly by interchanging the high- and low-speed sides of the wind tunnel, while maintaining the same velocities, and hence velocity ratio. This resulted in small changes in the initial boundary layer properties, and the perturbations present in the boundary layers were interchanged between the high- and low-speed sides for the two cases. The results indicate that, even with this relatively minor change in initial conditions, the near-field regions of the two cases differ significantly. The peak Reynolds stress levels in the near-field differ by up to 100 percent, and this is attributed to a difference in the location of the initial spanwise vortex roll-up. In addition, the positions and shapes of the individual streamwise vortical structures differ for the two cases, although the overall structures differ for the two cases, although the overall qualitative description of these structures is comparable. The subsequent reorganization and decay of the streamwise vortical structures is very similar for the two cases. As a result, in the far field, both mixing layers achieve similar structure, yielding comparable growth rates, Reynolds stress, distribution, and spectral content.
Aps Division of Fluid Dynamics Meeting Abstracts, 2003
Human speech is initiated as air passing through the glottis triggers self-sustained oscillations... more Human speech is initiated as air passing through the glottis triggers self-sustained oscillations of the vocal folds. These oscillations, caused by aerodynamic air pressures, glottal geometry and tissue properties, result in the glottis cyclically forming into a converging, straight, then diverging passage and finally closing. The varying shape of the glottis throughout the cycle causes different coherent structures to form. One such phenomenon evident in quasi-steady flow experiments is the skewing of the glottal jet towards one wall and attachment, i.e. the Coanda effect. It is not understood if the high frequency oscillations inherent in human phonation allow sufficient time for this oscillating jet to attach to the glottal wall, and thereby influence sound production. Unsteady flow through a high aspect ratio slot with an adjacent plate angled at 30 degrees to the streamwise direction was investigated. The driven, unsteady flow oscillation through the slot was chosen to represent known in-vivo velocity wave forms. Particle Image Velocimetry (PIV) was used to measure the phase-averaged development of the Coanda effect. The evolution of the unsteady Coanda effect over a range of frequencies typical of human phonation will be discussed.
Secondary flow structures were investigated in a 180-degree circular bend under physiological (pu... more Secondary flow structures were investigated in a 180-degree circular bend under physiological (pulsatile) flow conditions with a stent model installed upstream of the bend. Upstream Reynolds number ranged from 200 to 1400 and the cardiac cycle period was scaled to match the physiological Womersley number, Wo=4.2. Experimental data were acquired using 2-D PIV at various cross-sectional planes along the bend. Similar to the results in absence of the stent model, symmetric counter-rotating vortex pairs were observed to develop during the cardiac cycle. In addition, transient unstable flow was initiated at the deceleration phase of the systolic peak (t/T=0.21). This complex flow is mainly attributable to perturbations induced by the stent model. It is characterized by breakdown of Dean- and Lyne-type vortices into various multiple-scale vortices. The phase-averaged flow fields were analyzed using the proper orthogonal decomposition (POD) method to gain further insight regarding the stru...
43rd AIAA Aerospace Sciences Meeting and Exhibit, 2005
Large eddy simulations (LES) of low-speed, wall-bounded turbulent flows were conducted by numeric... more Large eddy simulations (LES) of low-speed, wall-bounded turbulent flows were conducted by numerically integrating the compressible Navier-Stokes equations in a generalized curvilinear coordinate system. An efficient numerical scheme based on a third-order ...
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