Guillermo Araya

The University of Texas at San Antonio | UTSA

Direct Numerical Simulation (DNS) databases of spatially-developing turbulent boundary layers (SDTBL) are scrutinized for detection of spatial/temporal periodic turbulent events. The databases involve incompressible and supersonic (Mach 2.86) flow regimes over isothermal and adiabatic wall thermal conditions at similar low Reynolds numbers (delta+...

We introduce Aquila-LCS, GPU and CPU optimized object-oriented, in-house codes for volumetric particle advection and 3D Finite-Time Lyapunov Exponent (FTLE) and Finite-Size Lyapunov Exponent (FSLE) computations. The purpose is to analyze 3D Lagrangian Coherent Structures (LCS) in large Direct Numerical Simulation (DNS) data. Our technique uses adva...

In this study, the unsteady Reynolds-averaged Navier-Stokes (URANS) equations are employed in conjunction with the Menter Shear Stress Transport (SST)-Scale-Adaptive Simulation (SAS) turbulence model in compressible flow, with an unstructured mesh and complex geometry. While other scale-resolving approaches in space and time, such as direct numeric...

The solution of compressible flow equations is of interest with many aerospace engineering applications. Past literature has focused primarily on the solution of Computational Fluid Dynamics (CFD) problems with low-order finite element and finite volume methods. High-order methods are more the norm nowadays, in both a finite element and a finite vo...

We investigate the performance of numerically implicit subgrid-scale modeling provided by the well-known streamline upwind/Petrov-Galerkin (SUPG) stabilization for finite element discretization of advection-diffusion problems in a Large Eddy Simulation (iLES) approach. While its original purpose was to provide sufficient algorithmic dissipation for...

In this work, we introduce a scalable and efficient GPU-accelerated methodology for volumetric particle advection and finite-time Lyapunov exponent (FTLE) calculation, focusing on the analysis of Lagrangian coherent structures (LCS) in large-scale direct numerical simulation (DNS) datasets across incompressible, supersonic, and hypersonic flow regi...

In this work, we introduce a scalable and efficient GPU-accelerated methodology for volumetric particle advection and finite-time Lyapunov exponent (FTLE) calculation, focusing on the analysis of Lagrangian Coherent Structures (LCS) in large-scale Direct Numerical Simulation (DNS) datasets across incompressible, supersonic, and hypersonic flow regi...

Mixed reality technology, i.e., virtual (VR) and augmented (AR) reality, has spread from research laboratories to enter the homes of many. Further, the widespread adoption of these technologies has caught the scientific community's attention, which is constantly researching potential applications. Backed by the continued enhancement of high-perform...

An incoming canonical spatially developing turbulent boundary layer (SDTBL) over a 2-D curved hill is numerically investigated via the Reynolds-averaged Navier–Stokes (RANS) equations plus two eddy-viscosity models: the K w SST (henceforth SST) and the Spalart–Allmaras (henceforth SA) turbulence models. A spatially evolving thermal boundary layer h...

Summary: Study concave/convex wall curvature on supersonic/hypersonic SDTBL (Mach numbers up to 5) in a suite of high spatial/temporal resolution Direct Numerical Simulation (DNS) as well as Implicit Wall Resolved Large Eddy Simulation (iLES) at high Reynolds numbers. Research Objectives: 1) Evaluate the effect of: (i) wall-curvature driven press...

Study concave/convex wall curvature on supersonic/hypersonic SDTBL (Mach numbers up to 5) in a suite of high spatial/temporal resolution Direct Numerical Simulation (DNS) as well as Wall Resolved Large Eddy Simulation (LES) at high Reynolds numbers.

View Video Presentation: https://doi.org/10.2514/6.2022-3627.vid Lagrangian Coherent Structures (LCS) have recently received a significant attention due to its advantages over Eulerian coherent structure identification schemes. Transport barriers and transport enhancers as material surfaces are identified by LCS techniques and can be used to analyz...

The interaction of a turbulent, spatially developing crossflow with a transverse jet possesses several engineering and technological applications such as film cooling of turbine blades, exhaust plumes, thrust vector control, fuel injection, etc. Direct Numerical Simulation (DNS) of a jet in a crossflow under different streamwise pressure gradients...

We employ numerically implicit subgrid-scale modeling provided by the well-known streamlined upwind/Petrov–Galerkin stabilization for the finite element discretization of advection–diffusion problems in a Large Eddy Simulation (LES) approach. Whereas its original purpose was to provide sufficient algorithmic dissipation for a stable and convergent...

Military, space, and high-speed civilian applications will continue contributing to the renewed interest in compressible, high-speed turbulent boundary layers. To further complicate matters, these flows present complex computational challenges ranging from the pre-processing to the execution and subsequent post-processing of large-scale numerical s...

View Video Presentation: https://doi.org/10.2514/6.2022-0479.vid Large databases of Direct Numerical Simulation (DNS) of spatially-developing turbulent boundary layers (SDTBL) are scrutinized. The major purpose is to evaluate compressibility effects on power spectra of velocity fluctuations at the supersonic ($M_{\infty}$ = 2.86) and hypersonic ($M...

View Video Presentation: https://doi.org/10.2514/6.2022-0049.vid In the scenario of a curved hill, the main objective is to study a turbulent boundary layer for incoming horizontal turbulent airstream at 20 20m/s by reproducing the wind-tunnel geometry as in [1]. A two-dimensional CFD RANS is performed with scope in the curved hill where moderate a...

This video can be found at: https://www.uprm.edu/hpcvl/research/ or https://www.youtube.com/watch?v=Au6Sa-E0R3Q Unsteady 3D turbulent boundary layers that evolve along the flow direction exhibit a streamwise non-homogeneous condition and pose enormous computational challenges. The reasons are as follows: (i) full spectrum resolution of turbulence,...

This video can be found at: https://www.uprm.edu/hpcvl/research/ or https://www.youtube.com/watch?v=E1IM5gJDAsg Visualization techniques have substantially evolved in the last few decades, spanning all disciplines. In recent times, Virtual (VR) and Augmented Reality (AR) have revolutionized the way that visualization is carried out. Virtual Realit...

The importance of coherent structures in turbulent boundary layers has been extensively explored in the large corpora of available literature. Although their impact on heat, mass and passive/active scalar transport has been extensively documented, their dependency on the Mach number has not been widely explored. In the present work, we identify coh...

Hypersonic boundary layers are crucial in aerospace applications such as hypersonic glide vehicles, rockets and other advanced space vehicles. Hypersonic flows present unique transport phenomena including non-negligible flow compression/dilation, extra strain rates and large mo-mentum/thermal gradients, among others. In this paper, we compare the p...

Investigate concave/convex wall curvature on supersonic/hypersonic SDTBL (Mach numbers up to 5) in a suite of high spatial/temporal resolution Direct Numerical Simulation (DNS) as well as Wall Resolved Large Eddy Simulation(LES) at experimental Reynolds numbers. https://community.apan.org/wg/afosr/m/kathy/212328

High-speed, compressible, turbulent boundary layers will be continue to gain relevance in many military, space and future civilian applications. However, furthering our understanding of crucial aspects of such flows present complex computational challenges from the preparation to the execution of said simulations. For instance, a relatively modest...

Direct simulation of hypersonic spatially-developing turbulent boundary layers (SDTBL) was carried out over Zero-Pressure Gradient (ZPG) flat plates at a Mach number of 5 and at different wall thermal conditions: wall cooling, adiabatic and wall heating. The Reynolds number range (Re δ2) is approximately 300-1200, based on the momentum thickness, f...

The widespread availability of high-performance commodity computing hardware has enabled technologies such as Virtual Reality and Augmented Reality to come out of research laboratories and enter the homes of many. Further, the widespread adoption of these technologies has caught the attention of the scientific community which is constantly research...

https://gfm.aps.org/meetings/dfd-2020/5f5ea810199e4c091e67bd54

https://gfm.aps.org/meetings/dfd-2020/5f5ee065199e4c091e67bd88

https://gfm.aps.org/meetings/dfd-2020/5f5ea510199e4c091e67bd4f

Recent numerical predictions of turbulent boundary layers subject to very strong Favorable Pressure Gradient (FPG) with high spatial/temporal resolution, i.e. Direct Numerical Simulation (DNS), have shown a meaningful weakening of the Reynolds shear stresses with a lengthy logarithmic behavior [1] [2]. In the present study, assessment of the Shear...

Direct Numerical Simulation (DNS) of compressible spatially-developing turbulent boundary layers (SDTBL) is performed at a Mach number of 2.5 and low/high Reynolds numbers over isothermal Zero-Pressure Gradient (ZPG) flat plates. Turbulent inflow information is generated via a dynamic rescaling-recycling approach (J. Fluid Mech., 670, pp. 581-605,...

Unsteady 3D turbulent boundary layers that evolve along the flow direction exhibit a streamwise non-homogeneous condition and pose enormous computational challenges. The reasons are as follows: (i) full spectrum resolution of turbulence, (ii) accurate time-dependent inflow turbulence information, and (iii) compressibility effects. Moreover, account...

https://gfm.aps.org/meetings/dfd-2019/5d7fc746199e4c429a9b3096

Spatially-developing turbulent boundary layers (SDTBL) are very challenging to numerically model by virtue of appropriate and realistic turbulent inflow information needed. In fact, the problem becomes harder if the idea is to account for compressibility effects, i.e. high Mach-number flows. Direct Numerical Simulation (DNS) is a promising numerica...

Direct Numerical Simulation (DNS) of turbulent spatially-developing boundary layers is performed over an isothermal flat plate at several flow regimes: incompressible, supersonic (Mach 2.5), and hypersonic (Mach 5). Similar low Reynolds numbers are considered in all cases with the purpose of assessing flow compressibility on low/high order flow sta...

One of the key factors in simulating realistic wall-bounded flows at high Reynolds numbers is the selection of an appropriate turbulence model for the steady Reynolds Averaged Navier–Stokes equations (RANS) equations. In this investigation, the performance of several turbulence models was explored for the simulation of steady, compressible, turbule...

Visualization of the thermal field in highly accelerated spatially developing turbulent boundary layers is carried out. Direct Numerical Simulation with high spatial/temporal resolution is performed in sink flow-type boundary layer by prescribing a passive scalar with a Prandtl number of 0.71. The range of the momentum thickness Reynolds number is...

Direct Numerical Simulation (DNS) with high spatial and temporal resolution of a jet transversely issuing into a turbulent boundary layer subject to very strong favorable pressure gradient (FPG) has been performed. The analysis is done by prescribing accurate turbulent information (instantaneous velocity and temperature) at the inlet of a computati...

https://gfm.aps.org/meetings/dfd-2018/5b97f004b8ac31610362f38b

https://gfm.aps.org/meetings/dfd-2018/5b9802e9b8ac31610362f398

Video at the Gallery of Fluid Motion: High spatial/temporal resolution Direct Numerical Simulation (DNS) of a spatially-developing turbulent boundary layer with a passive scalar is performed. The initial turbulent flow in a zero pressure gradient (ZPG) boundary layer is subjected to a very strong favorable pressure gradient (FPG). The strong accele...

https://gfm.aps.org/meetings/dfd-2017/59b9a84bb8ac316d38841d0c

Direct Numerical Simulation (DNS) with high spatial/temporal resolution of spatially developing turbulent boundary layers subject to very strong favorable pressure gradient (FPG) has been performed. The sudden acceleration imposed to the flow provokes a significant attenuation of turbulent intensities (Araya et al. [4]), particularly, due to the do...

Incompressible jets transversely issuing into a spatially-developing turbulent boundary layer is one of the most challenging and crucial types of three dimensional flows due to its fluid-dynamic complexity and technological applications; for instance , film cooling of turbine blades, chimney plumes, fuel injection , etc. In this investigation, Dire...

Direct Numerical Simulations (DNS) of an incompressible turbulent channel flow with given local perturbations at the wall have been performed. Steady blowing is applied at the bottom wall by means of five spanwise jets. The perturbing vertical velocities are assigned spatial sinusoidal distributions (i.e., in the streamwise and spanwise directions)...

In this investigation, Direct Numerical Simulations (DNS) of turbulent spatially developing boundary layers (SDBL) with prescribed Very Strong Favorable Pressure Gradients (VSFPG) are performed by means of the Dynamic Multi-scale Approach (DMA) developed by Araya et al. JFM, 670:518–605, 2011 [1]. Although the prescription of an external VSFPG sign...

High-frequency (50 Hz) observational data from the 200-m tower data (Reese Technology Center, Texas) have been prescribed as inflow conditions into the NREL FAST code in order to evaluate the structural impacts of Low Level Jets (LLJs) on a typical commercial wind turbine. A vertical region of interest for the analysis of interaction LLJ–wind turbi...

A zero-pressure-gradient turbulent boundary layer flowing over a transitionally rough surface (24-grit sandpaper) with $k^{+}\approx 11$ and a momentum-thickness Reynolds number of approximately 2400 is studied using direct numerical simulation (DNS). Heat transfer between the isothermal rough surface and the turbulent flow with molecular Prandtl...

The importance of large scale motions (LSMs) on thermal transport in a turbulent channel flow at friction number of 394 is investigated. Two-point correlation analysis reveals that LSM which significantly contribute to turbulence kinetic energy and scalar transport is a reminiscent of a hairpin packet. Low-order mode representation of the original...

We have analyzed long-term wind speed time-series from five field sites up to a height of 300 m from the ground. Structure function-based scaling analysis has revealed that the scaling exponents in the mesoscale regime systematically depend on height. This anomalous behavior is likely caused by the buoyancy effects. In the framework of the extended...

Wind energy is becoming a reliable and affordable source of clean energy and is rapidly expanding to remote places around the world. A crucial input for wind farming prospect is the assessment of potential wind sites. Sites, especially remotely located, often do not have a wind resource map and thus lack credible historical records of wind resource...

Direct numerical simulation of highly accelerated turbulent boundary layers (TBLs) reveals that the Reynolds shear stress, u v + , monotonically decreases downstream and exhibits a logarithmic behaviour (e.g. −u v + = −(1/A uv) ln y + + B uv) in the mesolayer region (e.g. 50 y + 170). The thickness of the log layer of u v + increases with the strea...

The understanding of atmospheric flows is crucial in the analysis of dispersion of a contaminant or pollutant, wind energy and air-quality assessment to name a few. Additionally, the effects of complex terrain and associated orographic forcing are crucial in wind energy production. Furthermore, the use of the Reynolds-averaged Navier-Stokes (RANS)...

Low Level Jets (LLJs) are defined as regions of relatively strong winds in the lower part of the atmosphere. They typically occur between 100 and 1500 m above ground level (ABL) and can be found in every continent. In particular, LLJs are a common feature over the Great Plains in the United States. It has been reported that 75% of LLJs in the Great...

Direct Numerical Simulations (DNS) of spatially-developing turbulent thermal boundary layers under stratification are performed. It is well known that the transport phenomena of the flow is significantly affected by buoyancy, particularly in urban environmentswhere neutral, stable and unstable atmospheric boundary layers are encountered. In the pre...

Submitted for the DFD13 Meeting of The American Physical Society Modeling of the Gecko's skin microfibrillar structures using the Immersed Boundary method via DNS ISNARDO ARENAS, KENNETH CARRASQUILLO, U. of Puerto Rico, STEFANO LEONARDI, U. of Texas Dallas, GUILLERMO ARAYA, FAZLE HUSSAIN, LUCIANO CASTILLO, Texas Tech U. — There is a current interes...

An innovative method for prescribing turbulent thermal inflow information in spatially developing boundary layers under streamwise pressure gradients is introduced for attached flows. The approach is tested and validated in a suite of Direct Numerical Simulations (DNS) of thermal boundary layers for zero (ZPG) and adverse (APG) pressure gradients w...

Direct Numerical Simulations (DNS) of spatially-developing turbulent boundary layers with prescribed moderate and strong adverse pressure (APG) gradients are performed. A method for prescribing realistic turbulent velocity inflow boundary conditions is employed based on the on the dynamic multi-scale approach proposed by [1] [2]; and, it is an exte...

A dynamic method for prescribing realistic inflow boundary conditions is presented for simulations of spatially developing turbulent boundary layers subject to surface roughness. Direct Numerical Simulation (DNS) of a moderate Reynolds number, zero pressure gradient (ZPG) turbulent boundary layer was performed. The boundary layer was subjected to t...

Direct Numerical Simulations (DNS) of spatially-evolving turbulent boundary layers with prescribed very strong adverse pressure gradients with eventual separation are performed. The driven force behind this investigation is to analyze the interaction between the inner and outer layers in separated flows. Also, the outer peaks in velocity fluctuatio...

A new approach for simulating realistic turbulent information at the entrance of a computational domain, which considers a spatially evolving turbulent thermal boundary layer, is presented. According to the method proposed by Lund et al. [1], turbulent velocity data is predicted from an auxiliary simulator located prior to the principal domain; whi...

A dynamic method for prescribing realistic inflow boundary conditions is presented for simulations of spatially developing turbulent boundary layers. The approach is based on the rescaling–recycling method proposed by Lund, Wu & Squires (J. Comput. Phys, vol. 140, 1998, pp. 233–258) and the multi-scale method developed by Araya, Jansen & Castillo (...

Direct Numerical Simulations (DNS) of an incompressible turbulent channel flow with given local perturbations at the walls are performed. Steady and time-periodic blowing/suction are applied by means of narrow spanwise slots located at the lower and upper walls. Our previous investigations on time-periodic blowing/suction (Araya et al. (2008) and a...

A method for generating realistic turbulent velocity inlet boundary conditions is presented for simulations of spatially evolving turbulent boundary layers. The approach is based on the rescaling–recycling method proposed by Lund et al. (J. Comput. Phys. 140:233–258, 1998). The standard rescaling process requires prior knowledge about how the appro...

A Direct numerical simulation (DNS) of a high Reynolds number, zero pressure gradient, turbulent boundary layer (Reθ= 2400) subjected to sandpaper surface roughness is performed. The surface roughness is modeled with a roughness parameter k^+ ˜ 25 to match the experiments at similar Reynolds number and roughness distribution. The employed computati...

Direct Numerical Simulations of spatially-evolving turbulent boundary layers with strong favorable pressure gradients are performed. The driven force behind this investigation is elucidate the mechanisms responsible for the quasi-laminarization of the boundary layer. Budgets of the turbulent kinetic energy and the shear Reynolds stresses provide in...

Direct Numerical Simulations of spatially evolving turbulent boundary layers with prescribed strong adverse pressure gradients are performed. The driven force behind this investigation is to analyze the interaction between the inner and outer layers in adverse pressure gradient with eventual separation. A method for prescribing realistic turbulent...