scholarly journals A Graphics Processing Unit (GPU) Approach to Large Eddy Simulation (LES) for Transport and Contaminant Dispersion

Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 890
Author(s):  
Paul E. Bieringer ◽  
Aaron J. Piña ◽  
David M. Lorenzetti ◽  
Harmen J. J. Jonker ◽  
Michael D. Sohn ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Graphics Processing Unit ◽  
Urban Landscapes ◽  
Processing Unit ◽  
Contaminant Dispersion ◽  
Central Processing ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Graphics Processing ◽  
The Impact

Recent advances in the development of large eddy simulation (LES) atmospheric models with corresponding atmospheric transport and dispersion (AT&D) modeling capabilities have made it possible to simulate short, time-averaged, single realizations of pollutant dispersion at the spatial and temporal resolution necessary for common atmospheric dispersion needs, such as designing air sampling networks, assessing pollutant sensor system performance, and characterizing the impact of airborne materials on human health. The high computational burden required to form an ensemble of single-realization dispersion solutions using an LES and coupled AT&D model has, until recently, limited its use to a few proof-of-concept studies. An example of an LES model that can meet the temporal and spatial resolution and computational requirements of these applications is the joint outdoor-indoor urban large eddy simulation (JOULES). A key enabling element within JOULES is the computationally efficient graphics processing unit (GPU)-based LES, which is on the order of 150 times faster than if the LES contaminant dispersion simulations were executed on a central processing unit (CPU) computing platform. JOULES is capable of resolving the turbulence components at a suitable scale for both open terrain and urban landscapes, e.g., owing to varying environmental conditions and a diverse building topology. In this paper, we describe the JOULES modeling system, prior efforts to validate the accuracy of its meteorological simulations, and current results from an evaluation that uses ensembles of dispersion solutions for unstable, neutral, and stable static stability conditions in an open terrain environment.

scholarly journals Simulation of Cavitation Water Flows

2015 ◽  
Vol 2015 ◽  
pp. 1-16 ◽  
Author(s):  
Piroz Zamankhan
Keyword(s):  
Graphics Processing Unit ◽  
Three Dimensional ◽  
High Energy ◽  
Cfd Modeling ◽  
Processing Unit ◽  
Water Mixture ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Computational Fluid Dynamics Cfd ◽  
Graphics Processing

The air-water mixture from an artificially aerated spillway flowing down to a canyon may cause serious erosion and damage to both the spillway surface and the environment. The location of an aerator, its geometry, and the aeration flow rate are important factors in the design of an environmentally friendly high-energy spillway. In this work, an analysis of the problem based on physical and computational fluid dynamics (CFD) modeling is presented. The numerical modeling used was a large eddy simulation technique (LES) combined with a discrete element method. Three-dimensional simulations of a spillway were performed on a graphics processing unit (GPU). The result of this analysis in the form of design suggestions may help diminishing the hazards associated with cavitation.

Accuracy of large eddy simulation for turbulent flow by the finite element method

1998 ◽  
Vol 212 (7) ◽  
pp. 643-650
Author(s):  
T Uchiyama
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Large Eddy Simulation ◽  
Processing Unit ◽  
The Finite Element Method ◽  
Central Processing ◽  
Eddy Simulation ◽  
Advection Term ◽  
Large Eddy ◽  
Element Method

This paper investigates the computational accuracy and CPU (central processing unit) time of large eddy simulation (LES) for turbulent flows performed by the finite element method. The investigations are accomplished by simulating a fully developed turbulent channel flow, which was analysed by Kim et al. using the direct numerical simulation (DNS) technique. When the advection term is discretized in gradient form, the turbulence decays and disappears with the passage of time. In using a multipass algorithm to solve the velocity field, the numerical result obtained by discretizing the advection term in divergent form agrees very well with that of the DNS. The multipass algorithm with the number of iterations k = 2 and 3 predict almost the same results. Thus, the algorithm with k = 2, allowing calculation with less CPU time, is successfully applicable to LES.

scholarly journals Application of GPU-Based Large Eddy Simulation in Urban Dispersion Studies

Atmosphere ◽  
2018 ◽  
Vol 9 (11) ◽  
pp. 442 ◽  
Author(s):  
Gergely Kristóf ◽  
Bálint Papp
Keyword(s):  
Wind Tunnel ◽  
Large Eddy Simulation ◽  
Transient Flow ◽  
Transport Processes ◽  
Air Pollutant ◽  
Processing Unit ◽  
Urban Dispersion ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Impact

While large eddy simulation has several advantages in microscale air pollutant dispersion modelling, the parametric investigation of geometries is not yet feasible because of its relatively high computational cost. By assuming an analogy between heat and mass transport processes, we utilize a Graphics Processing Unit based software—originally developed for mechanical engineering applications—to model urban dispersion. The software allows for the modification of the geometry as well as the visualization of the transient flow and concentration fields during the simulation, thus supporting the analysis and comparison of different design concepts. By placing passive turbulence generators near the inlet, a numerical wind tunnel was created, capable of producing the characteristic velocity and turbulence intensity profiles of the urban boundary layer. The model results show a satisfactory agreement with wind tunnel experiments examining single street canyons. The effect of low boundary walls placed in the middle of the road and adjacent to the walkways was investigated in a wide parameter range, along with the impact made by the roof slope angle. The presented approach can be beneficially used in the early phase of simulation driven urban design, by screening the concepts to be experimentally tested or simulated with high accuracy models.

scholarly journals Numerical simulation of flattened heat pipe with double heat sources for CPU and GPU cooling application in laptop computers

2020 ◽  
Author(s):  
Wisoot Sanhan ◽  
Kambiz Vafai ◽  
Niti Kammuang-Lue ◽  
Pradit Terdtoon ◽  
Phrut Sakulchangsatjatai
Keyword(s):  
Experimental Data ◽  
Heat Pipe ◽  
Graphics Processing Unit ◽  
Processing Unit ◽  
Heat Sources ◽  
Final Thickness ◽  
Laptop Computers ◽  
Central Processing ◽  
Graphics Processing ◽  
Good Agreement

Abstract An investigation of the effect of the thermal performance of the flattened heat pipe on its double heat sources acting as central processing unit and graphics processing unit in laptop computers is presented in this work. A finite element method is used for predicting the flattening effect of the heat pipe. The cylindrical heat pipe with a diameter of 6 mm and the total length of 200 mm is flattened into three final thicknesses of 2, 3, and 4 mm. The heat pipe is placed under a horizontal configuration and heated with heater 1 and heater 2, 40 W in combination. The numerical model shows good agreement compared with the experimental data with the standard deviation of 1.85%. The results also show that flattening the cylindrical heat pipe to 66.7 and 41.7% of its original diameter could reduce its normalized thermal resistance by 5.2%. The optimized final thickness or the best design final thickness for the heat pipe is found to be 2.5 mm.

Compressible large eddy simulation of the unsteady evolution process in a LPT Cascade with incoming wakes

2020 ◽  
pp. 095441002096753
Author(s):  
Yunfei Wang ◽  
Huanlong Chen ◽  
Huaping Liu ◽  
Yanping Song ◽  
Fu Chen
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Boundary Layer Separation ◽  
Main Flow ◽  
Reynolds Stresses ◽  
Flow Area ◽  
Eddy Simulation ◽  
Reduced Frequency ◽  
Large Eddy ◽  
The Impact

An in-house large eddy simulation (LES) code based on three-dimensional compressible N-S equations is used to research the impact of incoming wakes on unsteady evolution characteristic in a low-pressure turbine (LPT) cascade. The Mach number is 0.4 and Reynolds number is 0.6 × 105 (based on the axial chord and outlet velocity). The reduced frequency of incoming wakes is Fred = 0 (without wakes), 0.37 and 0.74. A detailed analysis of Reynolds stresses and turbulent kinetic energy inside the boundary layer has been carried out. Particular consideration is devoted to the transport process of incoming wakes and the intermittent property of the unsteady boundary layer. With the increase of reduced frequency, the inhibiting effect of wakes on boundary layer separation gradually enhances. The separation at the rear part of the suction side is weakened and the separation point moves downstream. However, incoming wakes lead to an increase in dissipation and aerodynamic losses in the main flow area. Excessive reduced frequency ( Fred = 0.74) causes the main flow area to become one of the main source areas of loss. An optimal reduced frequency exists to minimize the aerodynamic loss of the linear cascade.

scholarly journals Modelling waving crops using large-eddy simulation: comparison with experiments and a linear stability analysis

2010 ◽  
Vol 652 ◽  
pp. 5-44 ◽  
Author(s):  
S. DUPONT ◽  
F. GOSSELIN ◽  
C. PY ◽  
E. DE LANGRE ◽  
P. HEMON ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Large Eddy Simulation ◽  
Linear Stability ◽  
Linear Stability Analysis ◽  
Coupled Model ◽  
Wind Flow ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Eddy Structures ◽  
The Impact

In order to investigate the possibility of modelling plant motion at the landscape scale, an equation for crop plant motion, forced by an instantaneous velocity field, is introduced in a large-eddy simulation (LES) airflow model, previously validated over homogeneous and heterogeneous canopies. The canopy is simply represented as a poroelastic continuous medium, which is similar in its discrete form to an infinite row of identical oscillating stems. Only one linear mode of plant vibration is considered. Two-way coupling between plant motion and the wind flow is insured through the drag force term. The coupled model is validated on the basis of a comparison with measured movements of an alfalfa crop canopy. It is also compared with the outputs of a linear stability analysis. The model is shown to reproduce the well-known phenomenon of ‘honami’ which is typical of wave-like crop motions on windy days. The wavelength of the main coherent waving patches, extracted using a bi-orthogonal decomposition (BOD) of the crop velocity fields, is in agreement with that deduced from video recordings. The main spatial and temporal characteristics of these waving patches exhibit the same variation with mean wind velocity as that observed with the measurements. However they differ from the coherent eddy structures of the wind flow at canopy top, so that coherent waving patches cannot be seen as direct signatures of coherent eddy structures. Finally, it is shown that the impact of crop motion on the wind dynamics is negligible for current wind speed values. No lock-in mechanism of coherent eddy structures on plant motion is observed, in contradiction with the linear stability analysis. This discrepancy may be attributed to the presence of a nonlinear saturation mechanism in LES.

scholarly journals Numerical modelling of microburst with Large-Eddy Simulation

2010 ◽  
Vol 10 (10) ◽  
pp. 24345-24370
Author(s):  
V. Anabor ◽  
U. Rizza ◽  
G. A. Degrazia ◽  
E. de Lima Nascimento
Keyword(s):  
Large Eddy Simulation ◽  
Time Scale ◽  
Doppler Radar ◽  
Leading Edge ◽  
Ring Vortex ◽  
Short Time Scale ◽  
Eddy Simulation ◽  
Cloud Models ◽  
Large Eddy ◽  
The Impact

Abstract. An isolated and stationary microburst is simulated using a 3-D time-dependent, high resolution Large-Eddy Simulation (LES) model. The microburst downdraft is initiated by specifying a simplified cooling source at the top of the domain near 2 km. The modelled time scale for this damaging wind (30 m/s) is of order of few min with a spatial scale enclosing a region with 500 m radius around the impact point. These features are comparable with results obtained from full-cloud models. The simulated flow shows the principal features observed by Doppler radar and others observational full-scale downburst events. In particular are observed the expansion of the primary and secondary cores, the presence of the ring vortex at the leading edge of the cool outflow, and finally an accelerating outburst of surface winds. This result evidences the capability of LES to reproduce complexes phenomena like a Microburst and indicates the potential of LES for utilization in atmospheric phenomena situated below the storm scale and above the microscale, which generally involves high velocities in a short time scale.

ALGORITHM OF SKELETON-BASED STATIC HAND GESTURE RECOGNITION

2020 ◽  
pp. 13-22
Author(s):  
D. A. Kalina ◽  
R. V. Golovanov ◽  
D. V. Vorotnev
Keyword(s):  
Gesture Recognition ◽  
Graphics Processing Unit ◽  
Recognition System ◽  
Machine Learning Algorithms ◽  
Support Vector ◽  
Processing Unit ◽  
The Novel ◽  
Central Processing ◽  
Graphics Processing ◽  
Artificial Network

We present the monocamera approach of static hand gestures recognition based on skeletonization. The problem of creating skeleton of the human’s hand, as well as body, became solvable a few years ago after inventing so called convolutional pose machines – the novel architecture of artificial neural network. Our solution uses such kind of pretrained convolutional artificial network for extracting hand joints keypoints with further skeleton reconstruction. In this work we also propose special skeleton descriptor with proving its stability and distinguishability in terms of classification. We considered a few widespread machine learning algorithms to build and verify different classifiers. The quality of the classifier’s recognition is estimated using the wellknown Accuracy metric, which identified that classical SVM (Support Vector Machines) with radial basis kernel gives the best results. The testing of the whole system was conducted using public databases containing about 3000 of test images for more than 10 types of gestures. The results of a comparative analysis of the proposed system with existing approaches are demonstrated. It is shown that our gesture recognition system provides better quality in comparison with existing solutions. The performance of the proposed system was estimated for two configurations of standard personal computer: with CPU (Central Processing Unit) only and with GPU (Graphics Processing Unit) in addition where the latest one provides realtime processing with up to 60 frames per second. Thus we demonstrate that the proposed approach can find an application in the practice.

scholarly journals Subgrid-scale models and large-eddy simulation of oxygen stream disintegration and mixing with a hydrogen or helium stream at supercritical pressure

2011 ◽  
Vol 679 ◽  
pp. 156-193 ◽  
Author(s):  
EZGI S. TAŞKINOĞLU ◽  
JOSETTE BELLAN
Keyword(s):  
Heat Flux ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Correction Term ◽  
A Priori ◽  
Supercritical Pressure ◽  
Subgrid Scale ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Impact

For flows at supercritical pressure, p, the large-eddy simulation (LES) equations consist of the differential conservation equations coupled with a real-gas equation of state, and the equations utilize transport properties depending on the thermodynamic variables. Compared to previous LES models, the differential equations contain not only the subgrid-scale (SGS) fluxes but also new SGS terms, each denoted as a ‘correction’. These additional terms, typically assumed null for atmospheric pressure flows, stem from filtering the differential governing equations and represent differences, other than contributed by the convection terms, between a filtered term and the same term computed as a function of the filtered flow field. In particular, the energy equation contains a heat-flux correction (q-correction) which is the difference between the filtered divergence of the molecular heat flux and the divergence of the molecular heat flux computed as a function of the filtered flow field. We revisit here a previous a priori study where we only had partial success in modelling the q-correction term and show that success can be achieved using a different modelling approach. This a priori analysis, based on a temporal mixing-layer direct numerical simulation database, shows that the focus in modelling the q-correction should be on reconstructing the primitive variable gradients rather than their coefficients, and proposes the approximate deconvolution model (ADM) as an effective means of flow field reconstruction for LES molecular heat-flux calculation. Furthermore, an a posteriori study is conducted for temporal mixing layers initially containing oxygen (O) in the lower stream and hydrogen (H) or helium (He) in the upper stream to examine the benefit of the new model. Results show that for any LES including SGS-flux models (constant-coefficient gradient or scale-similarity models; dynamic-coefficient Smagorinsky/Yoshizawa or mixed Smagorinsky/Yoshizawa/gradient models), the inclusion of the q-correction in LES leads to the theoretical maximum reduction of the SGS molecular heat-flux difference; the remaining error in modelling this new subgrid term is thus irreducible. The impact of the q-correction model first on the molecular heat flux and then on the mean, fluctuations, second-order correlations and spatial distribution of dependent variables is also demonstrated. Discussions on the utilization of the models in general LES are presented.

scholarly journals Graphics processing unit implementation of the F-statistic for continuous gravitational wave searches

2021 ◽  
Author(s):  
Liam Dunn ◽  
Patrick Clearwater ◽  
Andrew Melatos ◽  
Karl Wette
Keyword(s):  
Gravitational Wave ◽  
Graphics Processing Units ◽  
Graphics Processing Unit ◽  
Computational Cost ◽  
Processing Unit ◽  
Central Processing ◽  
Long Baseline ◽  
Using Data ◽  
Graphics Processing ◽  
Gpu Implementation

Abstract The F-statistic is a detection statistic used widely in searches for continuous gravitational waves with terrestrial, long-baseline interferometers. A new implementation of the F-statistic is presented which accelerates the existing "resampling" algorithm using graphics processing units (GPUs). The new implementation runs between 10 and 100 times faster than the existing implementation on central processing units without sacrificing numerical accuracy. The utility of the GPU implementation is demonstrated on a pilot narrowband search for four newly discovered millisecond pulsars in the globular cluster Omega Centauri using data from the second Laser Interferometer Gravitational-Wave Observatory observing run. The computational cost is 17:2 GPU-hours using the new implementation, compared to 1092 core-hours with the existing implementation.

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