Eric Paterson - Academia.edu (original) (raw)

Papers by Eric Paterson

Ocean Engineering, Dec 1, 2015

Turbulent flow past the Glauert-Goldschmied body, a flow-control hump in a turbulent boundary lay... more Turbulent flow past the Glauert-Goldschmied body, a flow-control hump in a turbulent boundary layer, is studied numerically using detached-eddy simulation (DES), zonal detached-eddy simulation (ZDES), delayed detached-eddy simulation (DDES), and Reynolds-Averaged Navier-Stokes (RANS) modeling. The geometry is smooth so the downstream separation point is not set by facets of the geometry but is a function of the pressure gradient, a challenging condition for turbulence models. Comparisons to experimental data show that RANS with the Spalart-Allmaras turbulence model predicts the mean-field statistics well. The ZDES and DDES methods perform better than the DES formulation and are comparable to RANS in most statistics. An analysis of model behavior indicates that modeled stress depletion in the detached shear layer shortly after separation leads to loss of accuracy in the DES variants.

Asaio Journal, Mar 1, 2007

ABSTRACT An unsteady computational fluid dynamic methodology was developed so that design analyse... more ABSTRACT An unsteady computational fluid dynamic methodology was developed so that design analyses could be undertaken for devices such as the 50cc Penn State positive-displacement left ventricular assist device (LVAD). The piston motion observed in vitro was modeled, yielding the physiologic flow waveform observed during pulsatile experiments. Valve closure was modeled numerically by locally increasing fluid viscosity during the closed phase. Computational geometry contained Bjork-Shiley Monostrut mechanical heart valves in mitral and aortic positions. Cases for computational analysis included LVAD operation under steady-flow and pulsatile-flow conditions. Computations were validated by comparing simulation results with previously obtained in vitro particle image velocimetry (PIV) measurements. The steady portion of the analysis studied effects of mitral valve orientation, comparing the computational results with in vitro data obtained from mock circulatory loop experiments. The velocity field showed good qualitative agreement with the in vitro PIV data. The pulsatile flow simulations modeled the unsteady flow phenomena associated with a positive-displacement LVAD operating through several beat cycles. Flow velocity gradients allowed computation of the scalar wall strain rate, an important factor for determining hemodynamics of the device. Velocity magnitude contours compared well with PIV data throughout the cycle. Computational wall shear rates over the pulsatile cycle were found to be in the same range as wall shear rates observed in vitro.

Fluids, Dec 11, 2020

Electrochemical deposition (ECD) is a common method used in the field of microelectronics to grow... more Electrochemical deposition (ECD) is a common method used in the field of microelectronics to grow metallic coatings on an electrode. The deposition process occurs in an electrolyte bath where dissolved ions of the depositing material are suspended in an acid while an electric current is applied to the electrodes. The proposed computational model uses the finite volume method and the finite area method to predict copper growth on the plating surface without the use of a level set method or deforming mesh because the amount of copper layer growth is not expected to impact the fluid motion. The finite area method enables the solver to track the growth of the copper layer and uses the current density as a forcing function for an electric potential field on the plating surface. The current density at the electrolyte-plating surface interface is converged within each PISO (Pressure Implicit with Splitting Operator) loop iteration and incorporates the variance of the electrical resistance that occurs via the growth of the copper layer. This paper demonstrates the application of the finite area method for an ECD problem and additionally incorporates coupling between fluid mechanics, ionic diffusion, and electrochemistry.

35th Wind Energy Symposium, 2017

Fluids, 2020

The problem of simulating wakes in a stratified oceanic environment with active background turbul... more The problem of simulating wakes in a stratified oceanic environment with active background turbulence is considered. Anisotropic RANS turbulence models are tested against laboratory and eddy-resolving models of the problem. An important aspect of our work is to acknowledge that the environment is not quiescent; therefore, additional sources are included in the models to provide a non-zero background turbulence. The RANS models are found to reproduce some key features from the eddy-resolving and laboratory descriptions of the problem. Tests using the freestream sources show the intuitive result that background turbulence causes more rapid wake growth and decay.

Fluids, 2020

A modified set of governing differential equations for geophysical fluid flows is derived. All of... more A modified set of governing differential equations for geophysical fluid flows is derived. All of the simulation fields are decomposed into a nominal large-scale background state and a small-scale perturbation from this background, and the new system is closed by the assumption that the perturbation is one-way coupled to the background. The decomposition method, termed the multi-scale localized perturbation method (MSLPM), is then applied to the governing equations of stratified fluid flows, implemented in OpenFOAM, and exercised in order to simulate the interaction of a vertically-varying background shear flow with an axisymmetric perturbation in a turbulent ocean environment. The results demonstrate that the MSLPM can be useful in visualizing the evolution of a perturbation within a complex background while retaining the complex physics that are associated with the original governing equations. The simulation setup may also be simplified under the MSLPM framework. Further applicat...

Fluids, 2020

Electrochemical deposition (ECD) is a common method used in the field of microelectronics to grow... more Electrochemical deposition (ECD) is a common method used in the field of microelectronics to grow metallic coatings on an electrode. The deposition process occurs in an electrolyte bath where dissolved ions of the depositing material are suspended in an acid while an electric current is applied to the electrodes. The proposed computational model uses the finite volume method and the finite area method to predict copper growth on the plating surface without the use of a level set method or deforming mesh because the amount of copper layer growth is not expected to impact the fluid motion. The finite area method enables the solver to track the growth of the copper layer and uses the current density as a forcing function for an electric potential field on the plating surface. The current density at the electrolyte-plating surface interface is converged within each PISO (Pressure Implicit with Splitting Operator) loop iteration and incorporates the variance of the electrical resistance ...

Experiments in Fluids, 2018

Heat and Mass Transfer, 2015

Communications in Computational Physics, 2019

Feature identification is an important task in many fluid dynamics applications and diverse metho... more Feature identification is an important task in many fluid dynamics applications and diverse methods have been developed for this purpose. These methods are based on a physical understanding of the underlying behavior of the flow in the vicinity of the feature. Particularly, they rely on definition of suitable criteria (i.e. point-based or neighborhood-based derived properties) and proper selection of thresholds. For instance, among other techniques, vortex identification can be done through computing the Q-criterion or by considering the center of looping streamlines. However, these methods rely on creative visualization of physical idiosyncrasies of specific features and flow regimes, making them non-universal and requiring significant effort to develop. Here we present a physics-based, data-driven method capable of identifying any flow feature it is trained to. We use convolutional neural networks, a machine learning approach developed for image recognition, and adapt it to the problem of identifying flow features. The method was tested using mean flow fields from numerical simulations, where the recirculation region and boundary layer were identified in a two-dimensional flow through a convergent-divergent channel, and the horseshoe vortex was identified in three-dimensional flow over a wing-body junction. The novelty of the method is its ability to identify any type of feature, even distinguish between similar ones, without the need to explicitly define the physics (i.e. through development of suitable criterion and tunning of threshold). This provides a general method and removes the large burden placed on identifying new features. We expect this method can supplement existing techniques and allow for more automatic and discerning feature detection. The method can be easily extended to time-dependent flows, where it could be particularly impactful. For instance, it could be used in the identification of coherent structures in turbulent flows, a hindrance in the ongoing effort to establish a link between coherent structures and turbulence statistics.

Physical Review Fluids, 2017

Turbulence modeling is a critical component in numerical simulations of industrial flows based on... more Turbulence modeling is a critical component in numerical simulations of industrial flows based on Reynolds-averaged Navier-Stokes (RANS) equations. However, after decades of efforts in the turbulence modeling community, universally applicable RANS models with predictive capabilities are still lacking. Large discrepancies in the RANS-modeled Reynolds stresses are the main source that limits the predictive accuracy of RANS models. Identifying these discrepancies is of significance to possibly improve the RANS modeling. In this work, we propose a data-driven, physics-informed machine learning approach for reconstructing discrepancies in RANS modeled Reynolds stresses. The discrepancies are formulated as functions of the mean flow features. By using a modern machine learning technique based on random forests, the discrepancy functions are trained by existing DNS databases and then used to predict Reynolds stress discrepancies in different flows where data are not available. The proposed method is evaluated by two classes of flows: (1) fully developed turbulent flows in a square duct at various Reynolds numbers and (2) flows with massive separations. In separated flows, two training flow scenarios of increasing difficulties are considered: (1) the flow in the same periodic hills geometry yet at a lower Reynolds number, and (2) the flow in a different hill geometry with a similar recirculation zone. Excellent predictive performances were observed in both scenarios, demonstrating the merits of the proposed method.

17th AIAA Computational Fluid Dynamics Conference, 2005

In this paper, verification and validation analysis for pulsatile flow in a straight pipe is pres... more In this paper, verification and validation analysis for pulsatile flow in a straight pipe is presented. Numerical results were obtained using the finite volume method, and optimum grid density was determined using the Grid Convergence Index (GCI) calculation for the steady flow case. Based on the GCI calculation procedure we have developed a similar calculation for Time Convergence Index for the unsteady simulations. Transient computations were performed to obtain time dependent solutions of pulsating flow using three dierent time-steps and TCI was calculated to check time-step convergence. The numerical solution for the unsteady case was verified by comparing with accurate analytical solutions of Navier-Stokes equations for the pulsating flow in a pipe. Finally the numerical results were validated with experimental data. The results indicate that there is good agreement between the present results and analytical and experimental solutions. This paper stands as a good example for verification studies of unsteady CFD simulations where we have shown that TCI calculation can be applied in a similar procedure to grid convergence index calculation.

Notices of the American Mathematical Society, 2015

Flight MH370 disappeared less than an hour after takeoff on a flight from Kuala Lumpur to Beijing... more Flight MH370 disappeared less than an hour after takeoff on a flight from Kuala Lumpur to Beijing. The Boeing 777-200ER carried twelve crew members and 227 passengers. On March 24 the Malaysian Prime Minister announced that "It is therefore with deep sadness and regret that I must inform you that …Flight MH370 ended in the Southern Indian Ocean." Though the exact fate of Flight MH370 remains undetermined, the available evidence indicates a crash into the ocean. However, disturbing as this is, not all emergency water landings, referred to as "ditching" when they are controlled, end in tragedy. In the "Miracle on the Hudson," on January 15, 2009, Capt. Chelsey B. "Sully" Sullenberger and his crew successfully ditched US Airways Flight 1549, an Airbus A320-200, in the Hudson River after a loss of power due to a bird strike on takeoff from La Guardia Airport. There was no loss of life. Figure 1 and the video animation referenced on the second page of this article show our "representation" of a commercial airliner, a Boeing

ASME 2008 Summer Bioengineering Conference, Parts A and B, 2008

The 70cc LionHeart was developed for use in patients weighing more than 70 kg, which prevents its... more The 70cc LionHeart was developed for use in patients weighing more than 70 kg, which prevents its use in many women, smaller men, and children. Scaled-down devices have been prone to thrombus formation during animal testing [1, 2]. It is suspected that the increased level of thrombosis is related to changes in the flow field when scaling from the 70cc to the 50cc device. Low fluid shear stresses and high residence times are traits that are believed to influence thrombus formation and deposition within artificial blood pumps [1].

Ocean Engineering, Dec 1, 2015

Turbulent flow past the Glauert-Goldschmied body, a flow-control hump in a turbulent boundary lay... more Turbulent flow past the Glauert-Goldschmied body, a flow-control hump in a turbulent boundary layer, is studied numerically using detached-eddy simulation (DES), zonal detached-eddy simulation (ZDES), delayed detached-eddy simulation (DDES), and Reynolds-Averaged Navier-Stokes (RANS) modeling. The geometry is smooth so the downstream separation point is not set by facets of the geometry but is a function of the pressure gradient, a challenging condition for turbulence models. Comparisons to experimental data show that RANS with the Spalart-Allmaras turbulence model predicts the mean-field statistics well. The ZDES and DDES methods perform better than the DES formulation and are comparable to RANS in most statistics. An analysis of model behavior indicates that modeled stress depletion in the detached shear layer shortly after separation leads to loss of accuracy in the DES variants.

Asaio Journal, Mar 1, 2007

ABSTRACT An unsteady computational fluid dynamic methodology was developed so that design analyse... more ABSTRACT An unsteady computational fluid dynamic methodology was developed so that design analyses could be undertaken for devices such as the 50cc Penn State positive-displacement left ventricular assist device (LVAD). The piston motion observed in vitro was modeled, yielding the physiologic flow waveform observed during pulsatile experiments. Valve closure was modeled numerically by locally increasing fluid viscosity during the closed phase. Computational geometry contained Bjork-Shiley Monostrut mechanical heart valves in mitral and aortic positions. Cases for computational analysis included LVAD operation under steady-flow and pulsatile-flow conditions. Computations were validated by comparing simulation results with previously obtained in vitro particle image velocimetry (PIV) measurements. The steady portion of the analysis studied effects of mitral valve orientation, comparing the computational results with in vitro data obtained from mock circulatory loop experiments. The velocity field showed good qualitative agreement with the in vitro PIV data. The pulsatile flow simulations modeled the unsteady flow phenomena associated with a positive-displacement LVAD operating through several beat cycles. Flow velocity gradients allowed computation of the scalar wall strain rate, an important factor for determining hemodynamics of the device. Velocity magnitude contours compared well with PIV data throughout the cycle. Computational wall shear rates over the pulsatile cycle were found to be in the same range as wall shear rates observed in vitro.

Fluids, Dec 11, 2020

Electrochemical deposition (ECD) is a common method used in the field of microelectronics to grow... more Electrochemical deposition (ECD) is a common method used in the field of microelectronics to grow metallic coatings on an electrode. The deposition process occurs in an electrolyte bath where dissolved ions of the depositing material are suspended in an acid while an electric current is applied to the electrodes. The proposed computational model uses the finite volume method and the finite area method to predict copper growth on the plating surface without the use of a level set method or deforming mesh because the amount of copper layer growth is not expected to impact the fluid motion. The finite area method enables the solver to track the growth of the copper layer and uses the current density as a forcing function for an electric potential field on the plating surface. The current density at the electrolyte-plating surface interface is converged within each PISO (Pressure Implicit with Splitting Operator) loop iteration and incorporates the variance of the electrical resistance that occurs via the growth of the copper layer. This paper demonstrates the application of the finite area method for an ECD problem and additionally incorporates coupling between fluid mechanics, ionic diffusion, and electrochemistry.

35th Wind Energy Symposium, 2017

Fluids, 2020

The problem of simulating wakes in a stratified oceanic environment with active background turbul... more The problem of simulating wakes in a stratified oceanic environment with active background turbulence is considered. Anisotropic RANS turbulence models are tested against laboratory and eddy-resolving models of the problem. An important aspect of our work is to acknowledge that the environment is not quiescent; therefore, additional sources are included in the models to provide a non-zero background turbulence. The RANS models are found to reproduce some key features from the eddy-resolving and laboratory descriptions of the problem. Tests using the freestream sources show the intuitive result that background turbulence causes more rapid wake growth and decay.

Fluids, 2020

A modified set of governing differential equations for geophysical fluid flows is derived. All of... more A modified set of governing differential equations for geophysical fluid flows is derived. All of the simulation fields are decomposed into a nominal large-scale background state and a small-scale perturbation from this background, and the new system is closed by the assumption that the perturbation is one-way coupled to the background. The decomposition method, termed the multi-scale localized perturbation method (MSLPM), is then applied to the governing equations of stratified fluid flows, implemented in OpenFOAM, and exercised in order to simulate the interaction of a vertically-varying background shear flow with an axisymmetric perturbation in a turbulent ocean environment. The results demonstrate that the MSLPM can be useful in visualizing the evolution of a perturbation within a complex background while retaining the complex physics that are associated with the original governing equations. The simulation setup may also be simplified under the MSLPM framework. Further applicat...

Fluids, 2020

Electrochemical deposition (ECD) is a common method used in the field of microelectronics to grow... more Electrochemical deposition (ECD) is a common method used in the field of microelectronics to grow metallic coatings on an electrode. The deposition process occurs in an electrolyte bath where dissolved ions of the depositing material are suspended in an acid while an electric current is applied to the electrodes. The proposed computational model uses the finite volume method and the finite area method to predict copper growth on the plating surface without the use of a level set method or deforming mesh because the amount of copper layer growth is not expected to impact the fluid motion. The finite area method enables the solver to track the growth of the copper layer and uses the current density as a forcing function for an electric potential field on the plating surface. The current density at the electrolyte-plating surface interface is converged within each PISO (Pressure Implicit with Splitting Operator) loop iteration and incorporates the variance of the electrical resistance ...

Experiments in Fluids, 2018

Heat and Mass Transfer, 2015

Communications in Computational Physics, 2019

Feature identification is an important task in many fluid dynamics applications and diverse metho... more Feature identification is an important task in many fluid dynamics applications and diverse methods have been developed for this purpose. These methods are based on a physical understanding of the underlying behavior of the flow in the vicinity of the feature. Particularly, they rely on definition of suitable criteria (i.e. point-based or neighborhood-based derived properties) and proper selection of thresholds. For instance, among other techniques, vortex identification can be done through computing the Q-criterion or by considering the center of looping streamlines. However, these methods rely on creative visualization of physical idiosyncrasies of specific features and flow regimes, making them non-universal and requiring significant effort to develop. Here we present a physics-based, data-driven method capable of identifying any flow feature it is trained to. We use convolutional neural networks, a machine learning approach developed for image recognition, and adapt it to the problem of identifying flow features. The method was tested using mean flow fields from numerical simulations, where the recirculation region and boundary layer were identified in a two-dimensional flow through a convergent-divergent channel, and the horseshoe vortex was identified in three-dimensional flow over a wing-body junction. The novelty of the method is its ability to identify any type of feature, even distinguish between similar ones, without the need to explicitly define the physics (i.e. through development of suitable criterion and tunning of threshold). This provides a general method and removes the large burden placed on identifying new features. We expect this method can supplement existing techniques and allow for more automatic and discerning feature detection. The method can be easily extended to time-dependent flows, where it could be particularly impactful. For instance, it could be used in the identification of coherent structures in turbulent flows, a hindrance in the ongoing effort to establish a link between coherent structures and turbulence statistics.

Physical Review Fluids, 2017

Turbulence modeling is a critical component in numerical simulations of industrial flows based on... more Turbulence modeling is a critical component in numerical simulations of industrial flows based on Reynolds-averaged Navier-Stokes (RANS) equations. However, after decades of efforts in the turbulence modeling community, universally applicable RANS models with predictive capabilities are still lacking. Large discrepancies in the RANS-modeled Reynolds stresses are the main source that limits the predictive accuracy of RANS models. Identifying these discrepancies is of significance to possibly improve the RANS modeling. In this work, we propose a data-driven, physics-informed machine learning approach for reconstructing discrepancies in RANS modeled Reynolds stresses. The discrepancies are formulated as functions of the mean flow features. By using a modern machine learning technique based on random forests, the discrepancy functions are trained by existing DNS databases and then used to predict Reynolds stress discrepancies in different flows where data are not available. The proposed method is evaluated by two classes of flows: (1) fully developed turbulent flows in a square duct at various Reynolds numbers and (2) flows with massive separations. In separated flows, two training flow scenarios of increasing difficulties are considered: (1) the flow in the same periodic hills geometry yet at a lower Reynolds number, and (2) the flow in a different hill geometry with a similar recirculation zone. Excellent predictive performances were observed in both scenarios, demonstrating the merits of the proposed method.

17th AIAA Computational Fluid Dynamics Conference, 2005

In this paper, verification and validation analysis for pulsatile flow in a straight pipe is pres... more In this paper, verification and validation analysis for pulsatile flow in a straight pipe is presented. Numerical results were obtained using the finite volume method, and optimum grid density was determined using the Grid Convergence Index (GCI) calculation for the steady flow case. Based on the GCI calculation procedure we have developed a similar calculation for Time Convergence Index for the unsteady simulations. Transient computations were performed to obtain time dependent solutions of pulsating flow using three dierent time-steps and TCI was calculated to check time-step convergence. The numerical solution for the unsteady case was verified by comparing with accurate analytical solutions of Navier-Stokes equations for the pulsating flow in a pipe. Finally the numerical results were validated with experimental data. The results indicate that there is good agreement between the present results and analytical and experimental solutions. This paper stands as a good example for verification studies of unsteady CFD simulations where we have shown that TCI calculation can be applied in a similar procedure to grid convergence index calculation.

Notices of the American Mathematical Society, 2015

Flight MH370 disappeared less than an hour after takeoff on a flight from Kuala Lumpur to Beijing... more Flight MH370 disappeared less than an hour after takeoff on a flight from Kuala Lumpur to Beijing. The Boeing 777-200ER carried twelve crew members and 227 passengers. On March 24 the Malaysian Prime Minister announced that "It is therefore with deep sadness and regret that I must inform you that …Flight MH370 ended in the Southern Indian Ocean." Though the exact fate of Flight MH370 remains undetermined, the available evidence indicates a crash into the ocean. However, disturbing as this is, not all emergency water landings, referred to as "ditching" when they are controlled, end in tragedy. In the "Miracle on the Hudson," on January 15, 2009, Capt. Chelsey B. "Sully" Sullenberger and his crew successfully ditched US Airways Flight 1549, an Airbus A320-200, in the Hudson River after a loss of power due to a bird strike on takeoff from La Guardia Airport. There was no loss of life. Figure 1 and the video animation referenced on the second page of this article show our "representation" of a commercial airliner, a Boeing

ASME 2008 Summer Bioengineering Conference, Parts A and B, 2008

The 70cc LionHeart was developed for use in patients weighing more than 70 kg, which prevents its... more The 70cc LionHeart was developed for use in patients weighing more than 70 kg, which prevents its use in many women, smaller men, and children. Scaled-down devices have been prone to thrombus formation during animal testing [1, 2]. It is suspected that the increased level of thrombosis is related to changes in the flow field when scaling from the 70cc to the 50cc device. Low fluid shear stresses and high residence times are traits that are believed to influence thrombus formation and deposition within artificial blood pumps [1].