Anatomical airways parameters as length, diameter and angles have a strong effect on the flow dyn... more Anatomical airways parameters as length, diameter and angles have a strong effect on the flow dynamics. Aiming to explore the effect of variations of the bifurcation angle (BA) and carina rounding radius (CRR) of lower human airways on the respiratory processes, numerical simulations of airflow during inhalation and exhalation were performed using a synthetic bifurcation models. Geometries for the airways models were parameterized based on a set of different BA’s and several CRR’s. A range of Reynolds numbers (Re) relevant to the human breathing process were selected to analyzed the airflow behaviour. The numerical results show a significant influence of BA and the CRR on the development of the airflow within the airways, and therefore affecting some relevant features of the flow, namely the deformation of velocity profiles, alterations of pressure drop, the secondary flow patterns, and finally enhance or attenuation of wall shear stresses (WSS) appearing during the regular respirat...
The use of a synthetic jet as the flow control technique to modulate a turbulent incompressible r... more The use of a synthetic jet as the flow control technique to modulate a turbulent incompressible round jet was explored and assessed by numerical simulations. The flow response was characterised in terms of turbulent statistics and acoustic response in the far-field. A quasi-Direct Numerical Simulation (qDNS) strategy was used to predict the turbulent effects. The Ffowcs-Williams and Hawkings (FWH) acoustic analogy was employed to compute the far-field acoustic response. An amplification effect of the instabilities induced by the control jet was observed for some of the parameters explored. It was observed that the control technique allows controlling the axial distribution of the production and dissipation of turbulent kinetic energy, but with respect to the acoustic aspects, the appearance of a greater number of noise sources was observed, which in the far-field, resulted in an increase from 1 to 20 dB of the equivalent noise for the different operating parameters of the control te...
Resumen es: En este articulo se desarrollan varios ejemplos numericos sobre ecuaciones de reaccio... more Resumen es: En este articulo se desarrollan varios ejemplos numericos sobre ecuaciones de reaccion-difusion con dominio creciente, empleando el modelo de reaccion de...
Linearized Navier–Stokes equations are solved to investigate the impact on the growth of near-wal... more Linearized Navier–Stokes equations are solved to investigate the impact on the growth of near-wall turbulent streaks that arises from streamwise-travelling waves of spanwise wall velocity. The percentage change in streak amplification due to the travelling waves, over a range of wave parameters, is compared to published direct numerical simulation (DNS) predictions of turbulent skin-friction reduction; a clear correlation between the two is observed. Linearized simulations at a much higher Reynolds number, more relevant to aerospace applications, produce results that show no marked differences to those obtained at low Reynolds number. It is also observed that there is a close correlation between DNS data of drag reduction and a very simple characteristic of the ‘generalized’ Stokes layer generated by the streamwise-travelling waves.
Proceeding of Seventh International Symposium on Turbulence and Shear Flow Phenomena
ABSTRACT The near-wall streaks of a turbulent boundary layer are investigated using a modified ve... more ABSTRACT The near-wall streaks of a turbulent boundary layer are investigated using a modified version of a Low-Order Model (LOM)(Lockerby et al., 2005; Carpenter et al., 2007), which is based on the linearised Navier-Stokes equations (LNSE). The sensitivity of the ...
Schemes We present a computational study of the solution of the Falkner-Skan equation (a third-or... more Schemes We present a computational study of the solution of the Falkner-Skan equation (a third-order boundary value problem arising in boundary-layer theory) using high-order and high-order-compact finite differences schemes. There are a number of previously reported solution approaches that adopt a reduced-order system of equations, and numerical methods such as: shooting, Taylor series, Runge-Kutta and other semi-analytic methods. Interestingly, though, methods that solve the original non-reduced third-order equation directly are absent from the literature. Two high-order schemes are presented using both explicit (third-order) and implicit compact- difference (fourth-order) formulations on a semi-infinite domain; to our knowledge this is the first time that high-order finite difference schemes are presented to find numerical solutions to the non-reduced-order Falkner- Skan equation directly. This approach maintains the simplicity of Taylor-series coefficient matching methods, avoi...
Revista Facultad De Ingenieria-universidad De Antioquia, 2009
El presente articulo estudia el metodo Streamline Upwind Petrov Galerkin como tecnica de estabili... more El presente articulo estudia el metodo Streamline Upwind Petrov Galerkin como tecnica de estabilizacion de la solucion numerica de las ecuaciones diferenciales de adveccion-difusion-reaccion; se analiza el metodo a la luz de la naturaleza no auto adjunta del operador diferencial convectivo y de las transformaciones necesarias para la estabilizacion de la solucion por medio de la eliminacion del efecto no autoadjunto inducido por el termino convectivo. Se desarrollaron seis diversos ejemplos numericos, los cuales incluyen problemas de coeficientes variables, altamente convectivos, fuertemente reactivos, sistemas de ecuaciones diferenciales y soluciones transitorias. Se encuentra un excelente desempeno de esta tecnica de estabilizacion para todos los casos anteriormente mencionados, exceptuando los problemas con terminos reactivos fuertes.
In-silico models applied to bone remodeling are widely used to investigate bone mechanics, bone d... more In-silico models applied to bone remodeling are widely used to investigate bone mechanics, bone diseases, bone-implant interactions, and also the effect of treatments of bone pathologies. This article proposes a new methodology to solve the bone remodeling problem using one-dimensional (1D) elements to discretize trabecular structures more efficiently for 2D and 3D domains. An Euler integration scheme is coupled with the momentum equations to obtain the evolution of material density at each step. For the simulations, the equations were solved by using the finite element method, and two benchmark tests were solved varying mesh parameters. Proximal femur and calcaneus bone were selected as study cases given the vast research available on the topology of these bones, and compared with the anatomical features of trabecular bone reported in the literature. The presented methodology has proven to be efficient in optimizing topologies of lattice structures; It can predict the trend of form...
Anatomical airways parameters as length, diameter and angles have a strong effect on the flow dyn... more Anatomical airways parameters as length, diameter and angles have a strong effect on the flow dynamics. Aiming to explore the effect of variations of the bifurcation angle (BA) and carina rounding radius (CRR) of lower human airways on the respiratory processes, numerical simulations of airflow during inhalation and exhalation were performed using a synthetic bifurcation models. Geometries for the airways models were parameterized based on a set of different BA’s and several CRR’s. A range of Reynolds numbers (Re) relevant to the human breathing process were selected to analyzed the airflow behaviour. The numerical results show a significant influence of BA and the CRR on the development of the airflow within the airways, and therefore affecting some relevant features of the flow, namely the deformation of velocity profiles, alterations of pressure drop, the secondary flow patterns, and finally enhance or attenuation of wall shear stresses (WSS) appearing during the regular respirat...
The use of a synthetic jet as the flow control technique to modulate a turbulent incompressible r... more The use of a synthetic jet as the flow control technique to modulate a turbulent incompressible round jet was explored and assessed by numerical simulations. The flow response was characterised in terms of turbulent statistics and acoustic response in the far-field. A quasi-Direct Numerical Simulation (qDNS) strategy was used to predict the turbulent effects. The Ffowcs-Williams and Hawkings (FWH) acoustic analogy was employed to compute the far-field acoustic response. An amplification effect of the instabilities induced by the control jet was observed for some of the parameters explored. It was observed that the control technique allows controlling the axial distribution of the production and dissipation of turbulent kinetic energy, but with respect to the acoustic aspects, the appearance of a greater number of noise sources was observed, which in the far-field, resulted in an increase from 1 to 20 dB of the equivalent noise for the different operating parameters of the control te...
Resumen es: En este articulo se desarrollan varios ejemplos numericos sobre ecuaciones de reaccio... more Resumen es: En este articulo se desarrollan varios ejemplos numericos sobre ecuaciones de reaccion-difusion con dominio creciente, empleando el modelo de reaccion de...
Linearized Navier–Stokes equations are solved to investigate the impact on the growth of near-wal... more Linearized Navier–Stokes equations are solved to investigate the impact on the growth of near-wall turbulent streaks that arises from streamwise-travelling waves of spanwise wall velocity. The percentage change in streak amplification due to the travelling waves, over a range of wave parameters, is compared to published direct numerical simulation (DNS) predictions of turbulent skin-friction reduction; a clear correlation between the two is observed. Linearized simulations at a much higher Reynolds number, more relevant to aerospace applications, produce results that show no marked differences to those obtained at low Reynolds number. It is also observed that there is a close correlation between DNS data of drag reduction and a very simple characteristic of the ‘generalized’ Stokes layer generated by the streamwise-travelling waves.
Proceeding of Seventh International Symposium on Turbulence and Shear Flow Phenomena
ABSTRACT The near-wall streaks of a turbulent boundary layer are investigated using a modified ve... more ABSTRACT The near-wall streaks of a turbulent boundary layer are investigated using a modified version of a Low-Order Model (LOM)(Lockerby et al., 2005; Carpenter et al., 2007), which is based on the linearised Navier-Stokes equations (LNSE). The sensitivity of the ...
Schemes We present a computational study of the solution of the Falkner-Skan equation (a third-or... more Schemes We present a computational study of the solution of the Falkner-Skan equation (a third-order boundary value problem arising in boundary-layer theory) using high-order and high-order-compact finite differences schemes. There are a number of previously reported solution approaches that adopt a reduced-order system of equations, and numerical methods such as: shooting, Taylor series, Runge-Kutta and other semi-analytic methods. Interestingly, though, methods that solve the original non-reduced third-order equation directly are absent from the literature. Two high-order schemes are presented using both explicit (third-order) and implicit compact- difference (fourth-order) formulations on a semi-infinite domain; to our knowledge this is the first time that high-order finite difference schemes are presented to find numerical solutions to the non-reduced-order Falkner- Skan equation directly. This approach maintains the simplicity of Taylor-series coefficient matching methods, avoi...
Revista Facultad De Ingenieria-universidad De Antioquia, 2009
El presente articulo estudia el metodo Streamline Upwind Petrov Galerkin como tecnica de estabili... more El presente articulo estudia el metodo Streamline Upwind Petrov Galerkin como tecnica de estabilizacion de la solucion numerica de las ecuaciones diferenciales de adveccion-difusion-reaccion; se analiza el metodo a la luz de la naturaleza no auto adjunta del operador diferencial convectivo y de las transformaciones necesarias para la estabilizacion de la solucion por medio de la eliminacion del efecto no autoadjunto inducido por el termino convectivo. Se desarrollaron seis diversos ejemplos numericos, los cuales incluyen problemas de coeficientes variables, altamente convectivos, fuertemente reactivos, sistemas de ecuaciones diferenciales y soluciones transitorias. Se encuentra un excelente desempeno de esta tecnica de estabilizacion para todos los casos anteriormente mencionados, exceptuando los problemas con terminos reactivos fuertes.
In-silico models applied to bone remodeling are widely used to investigate bone mechanics, bone d... more In-silico models applied to bone remodeling are widely used to investigate bone mechanics, bone diseases, bone-implant interactions, and also the effect of treatments of bone pathologies. This article proposes a new methodology to solve the bone remodeling problem using one-dimensional (1D) elements to discretize trabecular structures more efficiently for 2D and 3D domains. An Euler integration scheme is coupled with the momentum equations to obtain the evolution of material density at each step. For the simulations, the equations were solved by using the finite element method, and two benchmark tests were solved varying mesh parameters. Proximal femur and calcaneus bone were selected as study cases given the vast research available on the topology of these bones, and compared with the anatomical features of trabecular bone reported in the literature. The presented methodology has proven to be efficient in optimizing topologies of lattice structures; It can predict the trend of form...
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