The study of the properties of fluids and gases in motion

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2
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2answers
59 views

9-point stencil finite difference Laplacian with variable diffusion coefficients

So I'm trying to implement a 9-point stencil discretization to the 2D difussion equation. The stencil is here. However, most of the literature deals with a Laplacian that has a constant diffusion ...
-2
votes
0answers
32 views

Best software for simulating fluid waves [on hold]

Hi I'm going to simulate the waves which caused by thermal fluctuation and I don't know what kind of software do I need!do you have any suggestions?I've tried COMSOL a little bit but I couldn't find ...
4
votes
1answer
54 views

transverse component for multidimensional advection in method of lines

So I inherited from some people a code that solves the advection-diffusion-reaction equation for a particular system. The original code was first implemented in 1D which worked fine in cartesian ...
2
votes
1answer
112 views

Darcy flow finite elements

The Darcy equations for porous media flow are given by: $\frac{\mu}{\kappa}\mathbf{u} - \nabla p = \mathbf{0}$ $\nabla\cdot\mathbf{u} = 0$ where $\kappa$ is the permeability and can in general be ...
1
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0answers
24 views

ANSYS Fluent: Defining External Force on a Cell Zone [closed]

I am using ANSYS Fluent 15 to simulate a case of fluid flow. In my case, I have three cell zones in my simulation, let's call them top, middle and bottom. My requirement is to put a vertical constant ...
2
votes
1answer
66 views

CFD turbulence modelling mean pressures vs peak pressures

I have been experimenting with using Autodesk CFD to investigate facade/ cladding pressures on a (rectangular) building, comparing results with cladding/ facades pressures pressures from design codes ...
2
votes
1answer
75 views

What are acceptable boundary conditions for porous media flow?

I am attempting to simulate fluid flow through a porous foam. I would like to have no-slip boundary conditions on part of the boundary and free flow conditions on the inlet and outlet. Right now I am ...
0
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0answers
53 views

How one can explain to have non-unique numerical solution at the interface boundary?

If the existed computational domain is divided into two pieces and developed numerical scheme is applied to these lets say right and left side domains of the interface individually to obtain two ...
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0answers
37 views

Computing Kolmogorov/Energy spectrum

I read a comment that you calculated energy spectrum for 3D DNS data obtained for isotropic turbulence which is equally spaced in all three directions. I have the same case, I am trying to do this ...
3
votes
3answers
182 views

Where do I begin learning CFD?

I am working on some CFD codes - generating adjoint of a CFD model, for example. My background however is in computer science. I have absolutely no clue what the model represents or what it is doing. ...
0
votes
1answer
50 views

Visualise data under Tecplot

I have a set of data that I need to visualise under Tecplot, the file format is for example: ...
0
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0answers
38 views

modify COMSOL codes

I am a physics student and I am planning to simulate microfluidics and capillary waves on a fluid film and I decided to use COMSOL. I am not so much aware of COMSOL abilities. I wonder if I can ...
1
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0answers
43 views

Conservation at grid interface in adaptive mesh refinement

I am using adaptive mesh refinement to solve one dimensional inviscid Burgers equation. However I am facing some difficulty to handle grid interfaces which are not uniform (coarse-fine grid ...
1
vote
1answer
85 views

openfoam - Programming customized PDEs

I am looking for a method to automatically solve custom PDEs on a custom control volume. Specifically I would like to solve equations similar (but not exactly alike) to: $$\frac{\partial y}{\partial ...
1
vote
1answer
96 views

GPU-enabled Lattice Boltzman solvers?

Is anybody aware of any GPU-enabled Lattice Boltzman solvers (preferably on C++/OpenCL and open-source) that would be recommended? I have found Advanced Simulation Library, but it seems to be very ...
0
votes
0answers
18 views

Plotting two different results in Tecplot together

I want to merge two results together and display them in Tecplot. For example: I have one DAT file which contains temperature of 64 points in each x and y direction and the other contains temperature ...
1
vote
2answers
114 views

How to deal with nonlinear term in Navier Stokes equations (finite element code)

I am trying to solve the Navier Stokes equations using the finite element method. I plan on using the pressure correction method to deal with the pressure and an implicit time stepping scheme for ...
0
votes
1answer
96 views

Adaptive mesh refinement basic conceptual problem

I am a beginner in adaptive mesh refinement (AMR). After I am done with the first two papers by Dr. Marsha Berger, I was trying to write my own code for a problem which has a parabolic partial ...
0
votes
1answer
52 views

Representation of polynomial order in CFD codes

I am currently working on a CFD code over a cubic grid. Now, the number of elements used in the simulation is decomposed among the number of processors. Each of those processors (a section of the ...
0
votes
4answers
222 views

Why are upwind schemes stable in convection flow calculation?

It is well known that upwind schemes are stable when calculating convection flows with $|\text{Pe}|>2$, $\text{Pe}$ is the Peclet number. Why is that, and why is central difference unstable? Is ...
1
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1answer
94 views

A Question About the Rhie-Chow Interpolation Used for Solving the Incompressible Navier-Stokes Equations on Unstructured Grids

When using the SIMPLE method on a mesh with a collocated variable arrangement, the following interpolation is used for the advecting velocities: \begin{equation} u_f = \overline{u}_f - ...
2
votes
2answers
111 views

Direct Numerical Simulation of reacting flows

I need to write a DNS code for simulating reacting flows in turbulent conditions. The code has to be highly scalable, because the computational cost of simulations is expected very large. My idea is ...
3
votes
1answer
98 views

2D Poisson Solver for Taylor Green Vortex Problem

I am trying to write a 2D Navier Stokes solver using an RK3 for time advancement in python. For debugging, I have converted the RK3 to an Euler step for simplicity. Checking my divergence for my ...
0
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0answers
47 views

Best way to average surface data or function data in 2d grid

I have pressure data on a 2D triangular surface. I can compute average(data). What is the best way to average the surface data?
5
votes
2answers
184 views

applications of computational geometry in fields such as CFD?

Out of curiosity, I was recently trying to search what skills are required to be successful as developer in scientific computing field (e.g. CFD or similar). And to do so, I was going to through ...
1
vote
1answer
75 views

alternatives to moving mesh technique

If one has to simulate oscillating plate/solid wall ( sinusoidal function of time) in a domain (a simple piston movement in 'y' direction), the obvious way would be scenario 1. For brevity, assume ...
1
vote
3answers
300 views

2D Stokes equation Code

Does anyone know where could I find a code (in Matlab or Mathematica, for example) for he Stokes equation in 2D? It has been solved numerically by so many people and referenced in so many paper that I ...
2
votes
1answer
134 views

Add User-defined/custom differential equations in OpenFoam (CFD)

I am new to OpenFoam. And I am trying to add a set (user defined) of differential equations to OpenFoam. I want to solve this user defined set of equations at each time point in addition to standard ...
0
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0answers
43 views

Can COMSOL solve a fluids problem given complicated N-S forcing terms as the input?

I am very much a novice at COMSOL but after pouring over its documentation, I have yet to build a working fluid model with this method. Here's the background: I am attempting to model a turbulent jet ...
0
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0answers
47 views

Help about Fluid-Fluid coupling techniques

I need a little help and advice with a project I want to do: the idea is to "couple" (I don't know whether I can call it like this) a conservative Navier-Stokes Solver (Fractional-step, 2nd order FDM) ...
0
votes
2answers
45 views

The “standard map” and Jupiter's red spot [closed]

Has there been an attempt to "explain" Jupiter's Red Spot via what is known as the standard map in chaos theory? I cannot be the first to notice the visual similarities...       ...
0
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0answers
23 views

Computational time in fluent using PBM+REACTION

I am having a problem of huge computation time. My system is a reaction, nucleation and growth. Time step i have taken is 10^-6 sec. it takes 10 minutes to reach 10^-2 sec. It will nearly take 70 ...
1
vote
2answers
107 views

How to interpret/convert density in 2D simulations?

Density has units of $kg/m^3$. In simulations often scaling is done to deal with non-dimensional values, so the physical density is converted to the non-dimensional density so that it can be used in ...
1
vote
1answer
46 views

Value of density when there are no or very few neighbours in SPH simulation

Sorry for the noob question. I am trying to implement SPH using the directions shown in this paper. The density needs to be updated using the formula The smoothing kernel is If there are no ...
2
votes
2answers
248 views

Manufactured solution for pressure based 3d incompressible Navier-Stokes solver with wall boundaries

I already successfully verified my solver (SIMPLE-type FVM-method) with the following manufactured solution (3d Taylor-Green vortex) on the solution domain $[-1,1]^3$ with Dirichlet boundary ...
0
votes
1answer
173 views

How to solve Energy Balance equation by numerical method

Good Day I am new to heat transfer technique please give me some suggestion on solving energy balance equation $$a \frac{\partial T_p}{\partial t}=\frac{\partial}{\partial x}\left(b\frac{\partial ...
1
vote
2answers
123 views

How to prove the strong formulation for Discontinuous Galerkin is conservative?

I've been trying to figure out how to prove that the following equation is conservative $$\int_{D^k} \partial_t(u^k) v_j^k + \partial_x(f) v_j^k dx = [(f -f^*) v^k_j]_{x^k}^{x^{k+1}}$$ where $v_j^k$ ...
2
votes
0answers
89 views

Arbitrary Choosing of the Solution Domain - Navier Stokes and Manufactured Solutions

I want to verify a finite-volume solver (SIMPLE-Algorithm) for the incompressible Navier-Stokes equations by using a manufactured solution. I use Dirichlet boundary conditions for the velocity at all ...
4
votes
3answers
142 views

Variable viscosity Stokes equation

One very efficient way to solve Stokes equation with periodic boundary conditions \begin{equation} -\eta \nabla^{2} \bf{v} + \nabla p = f \\ \nabla \cdot \bf{v} = 0 \end{equation} is using the ...
3
votes
2answers
365 views

Solution blows up when using Runge-Kutta to solve simultaneous ODEs for liquid film equations

This is a continuation of a problem I asked over at physics exchange and math exchange. Basically I have two ODEs that I am solving in order to calculate the radial and tangential velocity of liquid ...
2
votes
1answer
205 views

What's the difference between grid-based and mesh-based methods for PDEs?

I am into computational fluid dynamics and so far I've found that the most common approaches to solve for the governing equations are Eulerian and Lagrangian. The former samples the domain at fixed ...
3
votes
1answer
64 views

Zero-k mode in Pseudo-spectral solution of Stokes Flow

I'm trying to solve a Stokes flow problem with a pseudo-spectral method in periodic boundary conditions. The equations of interest are $-\nabla^2 \bf{v} + \nabla p = \bf{f} \\ \nabla \cdot \bf{v} = ...
5
votes
1answer
144 views

ENO/WENO component-wise vs characteristic-wise

Can someone give some references to understand what's the differences between a component-wise and a characteristic-wise ENO scheme? If I'm right, the characteristic variables come from the ...
2
votes
2answers
88 views

Expected computational time for DNS computation of fluid flow

Using an established criterion involving capturing eddies down to the Kolmogorov length scale it can be reasoned that the order of grid points in the computational mesh needs to be $N^3 \ge Re^{9/4}$ ...
3
votes
1answer
323 views

Finite Element integration with tensor notation

While I was studying discontinuous finite element methods I found an integration of a Navier Stokes equation using tensorial notation. The equation is the following: $\mathbf{\bar {u}}_{t} + ...
2
votes
0answers
132 views

Finite Volume/difference scheme for 2d continuity equation

I am trying to solve the following 2D continuity equation on the rectangular domain [0,1]x[0,1] using the finite volume method. $\rho_t + \nabla \cdot (\rho v) = 0$ where the velocity $v =(v1,v2)$ is ...
0
votes
3answers
147 views

What Is The Intersection Between CFD and Computer Science

What Is The Intersection Between CFD and Computer Science... And.. How hard would it be to undertake a PHD in CFDs after an undergrad and masters in CompSci Many Thanks....
2
votes
2answers
104 views

Can the conservative form of the advection equation be re-written by replacing the velocity term with an integral over all other points in space?

Suppose I have a 1D advection equation in conservation (divergence) form $\partial_t u(x,t) = -\partial_x [v(x)u(x,t)],$ where $u$ is a conserved quantity in space, and $v$ gives the velocity of the ...
0
votes
0answers
71 views

Comsol - Make an stl file a domain for CFD

I need to do a CFD simulation with Comsol. I have an STL file with a mesh describing the surface of an object on which I would like to do some fluid dynamics simulation. As far as my understanding ...
1
vote
1answer
79 views

Finite Volume Method flux integration

I was reading through this document about FVM. I understood all up to the point where we have on page 15 the following $$(\bar u^{n+1}_i - \bar u^n_i) \Delta x + \int^{t^{n+1}}_{t^n} ...