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Papers by parham vatankhah

Research paper thumbnail of Computational Fluid Dynamics Simulations at Micro-Scale Stenosis for Microfluidic Thrombosis Model Characterization

Research paper thumbnail of Hemodynamic analysis for stenosis microfluidic model of thrombosis with refined computational fluid dynamics simulation

Scientific Reports

Disturbed blood flow has been increasingly recognized for its critical role in platelet aggregati... more Disturbed blood flow has been increasingly recognized for its critical role in platelet aggregation and thrombosis. Microfluidics with hump shaped contractions have been developed to mimic microvascular stenosis and recapitulate the prothrombotic effect of flow disturbance. However the physical determinants of microfluidic hemodynamics are not completely defined. Here, we report a refined computational fluid dynamics (CFD) simulation approach to map the shear rate (γ) and wall shear stress (τ) distribution in the stenotic region at high accuracy. Using ultra-fine meshing with sensitivity verification, our CFD results show that the stenosis level (S) is dominant over the bulk shear rate (γ0) and contraction angle (α) in determining γ and τ distribution at stenosis. In contrast, α plays a significant role in governing the shear rate gradient (γ′) distribution while it exhibits subtle effects on the peak γ. To investigate the viscosity effect, we employ a Generalized Power-Law model to...

Research paper thumbnail of Numerical optimization and inverse study of a microfluidic device for blood plasma separation

European Journal of Mechanics - B/Fluids, 2016

Abstract In this paper, a passive microfluidic device for continuous real time blood plasma separ... more Abstract In this paper, a passive microfluidic device for continuous real time blood plasma separation has been studied and optimized. A numerical model is used to solve both the fluid flow and the particles confined within it. Red blood cells are considered as particles with diameter of 7 μ m . A parametric study is performed in order to characterize the effect of different parameters on separation and purity efficiency. In this study, four different variables were introduced to design the microfluidic device for blood plasma separation including: the angle between the daughter channels and the main channel, the widths, the diffuse angle and the number of daughter channels. Results show that the separation and purity efficiency have an opposite trend. Since finding the optimal design, where both separation and purity efficiency are desirable, was the goal of this research, an optimization is performed by means of Pattern Search algorithm including all the variables. By means of optimization, it is shown that the performance of device can be improved considerably. Optimal design with separation efficiency of 83% and purity efficiency of 85% is achieved. Moreover, an inverse study has been done to calculate the design variables based on the desired separation and purity efficiency. According to related research, separation and purity efficiency were set to (40%, 53%) and (25%, 100%). Design variables were obtained with less than 1% and 4% error, respectively.

Research paper thumbnail of Analyzing mixing quality in a curved centrifugal micromixer through numerical simulation

Chemical Engineering and Processing, 2017

The Lab On a CD (LOCD), also known as Centrifugal Microfluidics, has evolved into a sophisticated... more The Lab On a CD (LOCD), also known as Centrifugal Microfluidics, has evolved into a sophisticated platform for performing biomedical assays due to its marvelous miniaturization and accurate simulation of biological reactions. Among the numerous applications of the LOCD is fluid mixing. In this paper a centrifugal, serpentine micromixer is simulated and reformed toward better mixing performance. The micromixer was chosen to be curved as a curved design was found to be thrice as functional and compact as a rectilinear design, mixing-wise. The two angular velocity and opening radius parameters were originally hypothesized to affect mixing performance. Effect of angular velocity was studied over a broad range starting from quite low values. It was gathered that with increasing angular velocity, mixing performance initially drops and upon reaching a minimum at a threshold angular velocity, begins to continuously increase. The threshold angular velocity was found to be the spot at which t...

Research paper thumbnail of A Computational Fluid Dynamics Protocol for The Hemodynamic Analysis of a Microfluidic Model of Thrombosis

Thrombosis is both attributed to biochemical agonists and mechanical stresses applied to platelet... more Thrombosis is both attributed to biochemical agonists and mechanical stresses applied to platelets. Whilst the effect of biochemical agonists has been extensively studied, the mechanosensitive factors remain poorly defined. Stenotic microfluidic channels mimic the narrowing vessels, providing the real-time observation of platelets under disturbed flow. Though the experimental analysis of platelets in disturbed flow confirms the mechanosensitive behavior of platelets, it cannot explicate detailed thresholds for platelet activation. Computational Fluid Dynamics (CFD) could be utilized alongside experimental analysis to characterize thresholds for platelet behavior under imposed shear stress. CFD simulations, however, are prone to uncertainties and errors which should be minimized to obtain compelling results. Hereby, we have presented a CFD protocol for researchers in the field of microfluidic and hemodynamic studies.

Research paper thumbnail of Parametric study on mixing process in an in-plane spiral micromixer utilizing chaotic advection

Research paper thumbnail of Numerical Simulation of Heat Transfer in Mixed Electroosmotic Pressure-Driven Flow in Straight Microchannels

Journal of Thermal Science and Engineering Applications, 2015

This paper investigates two-dimensional, time-independent elecroosmotic pressure-driven flow gene... more This paper investigates two-dimensional, time-independent elecroosmotic pressure-driven flow generated by a direct current electric potential with asymmetrical and symmetrical zeta potential distributions along the microchannel walls. Fluid flow through the horizontal microchannel is simulated using a numerical method. Two different cases are proposed to study the effect of electric potential on the flow field. First, negative electric potential is applied on the microchannel walls. In this case, large segments with negative electric potential are initially placed on the first half of the microchannel walls with two different arrangements. Afterward, smaller segments with negative electric potential are placed on the microchannel walls. Next, negative electric potential is replaced by positive electric potential on the microchannel walls in the similar manner. It is shown that applying positive potential on the walls contributes to the localized circular flows within the microchanne...

Research paper thumbnail of Computational Fluid Dynamics Simulations at Micro-Scale Stenosis for Microfluidic Thrombosis Model Characterization

Research paper thumbnail of Hemodynamic analysis for stenosis microfluidic model of thrombosis with refined computational fluid dynamics simulation

Scientific Reports

Disturbed blood flow has been increasingly recognized for its critical role in platelet aggregati... more Disturbed blood flow has been increasingly recognized for its critical role in platelet aggregation and thrombosis. Microfluidics with hump shaped contractions have been developed to mimic microvascular stenosis and recapitulate the prothrombotic effect of flow disturbance. However the physical determinants of microfluidic hemodynamics are not completely defined. Here, we report a refined computational fluid dynamics (CFD) simulation approach to map the shear rate (γ) and wall shear stress (τ) distribution in the stenotic region at high accuracy. Using ultra-fine meshing with sensitivity verification, our CFD results show that the stenosis level (S) is dominant over the bulk shear rate (γ0) and contraction angle (α) in determining γ and τ distribution at stenosis. In contrast, α plays a significant role in governing the shear rate gradient (γ′) distribution while it exhibits subtle effects on the peak γ. To investigate the viscosity effect, we employ a Generalized Power-Law model to...

Research paper thumbnail of Numerical optimization and inverse study of a microfluidic device for blood plasma separation

European Journal of Mechanics - B/Fluids, 2016

Abstract In this paper, a passive microfluidic device for continuous real time blood plasma separ... more Abstract In this paper, a passive microfluidic device for continuous real time blood plasma separation has been studied and optimized. A numerical model is used to solve both the fluid flow and the particles confined within it. Red blood cells are considered as particles with diameter of 7 μ m . A parametric study is performed in order to characterize the effect of different parameters on separation and purity efficiency. In this study, four different variables were introduced to design the microfluidic device for blood plasma separation including: the angle between the daughter channels and the main channel, the widths, the diffuse angle and the number of daughter channels. Results show that the separation and purity efficiency have an opposite trend. Since finding the optimal design, where both separation and purity efficiency are desirable, was the goal of this research, an optimization is performed by means of Pattern Search algorithm including all the variables. By means of optimization, it is shown that the performance of device can be improved considerably. Optimal design with separation efficiency of 83% and purity efficiency of 85% is achieved. Moreover, an inverse study has been done to calculate the design variables based on the desired separation and purity efficiency. According to related research, separation and purity efficiency were set to (40%, 53%) and (25%, 100%). Design variables were obtained with less than 1% and 4% error, respectively.

Research paper thumbnail of Analyzing mixing quality in a curved centrifugal micromixer through numerical simulation

Chemical Engineering and Processing, 2017

The Lab On a CD (LOCD), also known as Centrifugal Microfluidics, has evolved into a sophisticated... more The Lab On a CD (LOCD), also known as Centrifugal Microfluidics, has evolved into a sophisticated platform for performing biomedical assays due to its marvelous miniaturization and accurate simulation of biological reactions. Among the numerous applications of the LOCD is fluid mixing. In this paper a centrifugal, serpentine micromixer is simulated and reformed toward better mixing performance. The micromixer was chosen to be curved as a curved design was found to be thrice as functional and compact as a rectilinear design, mixing-wise. The two angular velocity and opening radius parameters were originally hypothesized to affect mixing performance. Effect of angular velocity was studied over a broad range starting from quite low values. It was gathered that with increasing angular velocity, mixing performance initially drops and upon reaching a minimum at a threshold angular velocity, begins to continuously increase. The threshold angular velocity was found to be the spot at which t...

Research paper thumbnail of A Computational Fluid Dynamics Protocol for The Hemodynamic Analysis of a Microfluidic Model of Thrombosis

Thrombosis is both attributed to biochemical agonists and mechanical stresses applied to platelet... more Thrombosis is both attributed to biochemical agonists and mechanical stresses applied to platelets. Whilst the effect of biochemical agonists has been extensively studied, the mechanosensitive factors remain poorly defined. Stenotic microfluidic channels mimic the narrowing vessels, providing the real-time observation of platelets under disturbed flow. Though the experimental analysis of platelets in disturbed flow confirms the mechanosensitive behavior of platelets, it cannot explicate detailed thresholds for platelet activation. Computational Fluid Dynamics (CFD) could be utilized alongside experimental analysis to characterize thresholds for platelet behavior under imposed shear stress. CFD simulations, however, are prone to uncertainties and errors which should be minimized to obtain compelling results. Hereby, we have presented a CFD protocol for researchers in the field of microfluidic and hemodynamic studies.

Research paper thumbnail of Parametric study on mixing process in an in-plane spiral micromixer utilizing chaotic advection

Research paper thumbnail of Numerical Simulation of Heat Transfer in Mixed Electroosmotic Pressure-Driven Flow in Straight Microchannels

Journal of Thermal Science and Engineering Applications, 2015

This paper investigates two-dimensional, time-independent elecroosmotic pressure-driven flow gene... more This paper investigates two-dimensional, time-independent elecroosmotic pressure-driven flow generated by a direct current electric potential with asymmetrical and symmetrical zeta potential distributions along the microchannel walls. Fluid flow through the horizontal microchannel is simulated using a numerical method. Two different cases are proposed to study the effect of electric potential on the flow field. First, negative electric potential is applied on the microchannel walls. In this case, large segments with negative electric potential are initially placed on the first half of the microchannel walls with two different arrangements. Afterward, smaller segments with negative electric potential are placed on the microchannel walls. Next, negative electric potential is replaced by positive electric potential on the microchannel walls in the similar manner. It is shown that applying positive potential on the walls contributes to the localized circular flows within the microchanne...