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19 votes

What is the difference between FEA and CFD?

CFD (computational fluid dynamics) includes any numerical method used to solve fluid flow problems. FEA (finite element analysis) is one numerical method for solving partial differential equations, ...
alephzero's user avatar
  • 12.5k
4 votes

Question about bounday layer thickness?

The greater the length of the flat plate, the more contact area there is with the fluid. Consequently, the fluid near the start of the plate has had less viscous friction forces acting on it than the ...
Paul's user avatar
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3 votes

How to determine time taken for tyre to deflate using CFD analysis?

I don't think CFD is the right tool. You can use an orifice equation, say from ASME, to calculate flow rate from inner and outer pressure. This takes the form of: $$\dot{m}=\frac{EC_D}{\sqrt{1-\beta^4}...
RC_23's user avatar
  • 781
3 votes

What is the best method to generate heat from a compressed air canister?

One possibility would be to use the air to drive a turbine (probably a radial turbine as they are used in turbochargers). The turbine could be connected to a generator and the generator to a resistor. ...
rul30's user avatar
  • 1,192
3 votes

Should I expect fluid velocity within a pipe to increase beyond the inlet velocity?

The mean velocity of the fluid must be constant, if the fluid is incompressible and the area is constant. But since you are modelling a viscous fluid, there will be a velocity profile over a cross ...
alephzero's user avatar
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2 votes

How to measure turbulence parameters experimentally?

One method is to use a hot wire anemometer. This (about 50 pages, ignoring the product-specific stuff at the end) is a good read. In principle, a hot wire anemometer is simply a metal wire (often ...
alephzero's user avatar
  • 12.5k
2 votes

What is the best method to generate heat from a compressed air canister?

Any engine that can run on compressed air will do this. There are quite a few, but as an example imagine a cylinder that has a bit of compressed air in it. The pressure will push on the piston doing ...
Gunchars's user avatar
  • 151
1 vote

Centrifugal pump head-flow prediction with CFD

It is common to use CFD simulation of a given pump geometry to predict a performance curve for the pumps volumetric flow rate vs. a range of pressure difference (head) that the pump is seeing. ...
TheJoyOfSimulation's user avatar
1 vote

Is supersonic flow not possible in a venturi tube?

Supersonic flow is possible in a Venturi tube, just not at the throat. In order for the flow at the throat to be supersonic, there would have to be a location somewhere between the upstream (...
Daniel Hatton's user avatar
1 vote

How to compute wall heat flux q with just wall temperature

If you are looking just for heat flux (aka heat flux density, heat-flow density or heat flow rate intensity) and you know that the heat rate is 128 W, then the heat flux is just: $$\phi_q = \frac{\...
NMech's user avatar
  • 24.4k
1 vote

How to determine the force to empty a syringe containing high-viscosity fluid?

I will make two assumptions from your question: horizontal orientation of nozzle + piston in order to discard hydrostatic pressure, since a vertical orientation would modify the force required to ...
TaglieriSao's user avatar
1 vote

How to deal with time derivative of speed toward time in staggered grid in CFD?

I can't believe that I forgot in SIMPLE we first treat $p$ as known. The we should integrate this equation over the u-control volume. Because the time term no relation to $x$ and $y$, so it's simply ...
kilasuelika's user avatar
1 vote

VTOL Aircraft Take-Off Mechanics Question

Yes as you guess the flaps and stabilizer being down are to take advantage of the ground effect and scoop more air deflected by the ground at take off and also as you guessed again they help smooth ...
kamran's user avatar
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1 vote
Accepted

Pressure Coefficient with a Minima of 0 on Compressor Airfoils in Cascade

In the report $P$ is the total pressure and $p$ is the static pressure. See the page in the report before the one you attached in the OP. With that definition, $S$ will be zero at the stagnation ...
alephzero's user avatar
  • 12.5k
1 vote

Why is Rocket Nozzle CFD done in 2D instead of 3D?

It isn't really done in 2D. It is done in pseudo 3D. The actual annular areas are factored in. It is primarily based on a uniformity assumption that the gas dynamics are the same all around the nozzle ...
Phil Sweet's user avatar
  • 4,765
1 vote

How do drag and downforce in a rear spoiler of a car vary with angle of attack?

It isn't clear from the question whether you are using a flat plate spoiler like in NASCAR or an inverted airfoil like in Formula 1. For flat plate spoilers a big part of what they are doing is to ...
Eric S's user avatar
  • 915
1 vote

What does mesh topology mean?

Depending on the context, mesh topology is the cell or mesh density and how it changes across the whole calculation field. To get detail then the computational area is divided into cells - more cells ...
Solar Mike's user avatar
  • 15.9k
1 vote

Turbulence model for low reynolds problem

I solved my problem. I refined the mesh. Part of the problem was the high aspect ratio of my cells, because my tube is very thin in comparison to the length. I have solved the problem laminar and then ...
Gesetzt's user avatar
  • 93
1 vote

What is the best method to generate heat from a compressed air canister?

Since the expanding air will try to cool it's immediate surroundings, you need isolate the expanded air supply from the area to be heated. As long as you have a heat sink, you can use an air motor to ...
Phil Sweet's user avatar
  • 4,765
1 vote

Smoothed Particle Hydrodynamics (SPH) Vs. Large Eddy Simulation (LES) for Gearboxes

SPH is one of two different particle methods. SPH has limitations as discussed above. You may also want to look at Moving Particle Semi-Implicit method (MPS). This method is better for ...
MeAndCFD's user avatar
1 vote

Smoothed Particle Hydrodynamics (SPH) Vs. Large Eddy Simulation (LES) for Gearboxes

I don't use SPH for fluid dynamics personally, but I've seen some presentations where it has been used for high strain rate material behavior which shares some effects (and equations) with standard ...
Robin's user avatar
  • 679
1 vote
Accepted

How to model the inside of a server for CFD and thermal studies?

Your options are a bit limited. Either you get the model from Dell, or you model it yourself. Getting the model is a long shot, but if you are a really big customer that might happen. However this ...
joojaa's user avatar
  • 3,577
1 vote

What is a good method (equation) for locally refining a 1D grid at each end?

I'm assuming that your equation is only used to define the spacing from an end to the middle, after which you mirror it. Instead of dx1, write L / N, where L is the total length. Now you have x(i) ...
elliot svensson's user avatar
1 vote
Accepted

Steady state approximation for compressible fluid flow (manifolds and other pressure vessels)

We model the system simply for small mass flow rates compared to the size of the vessel simply: At point 1, the pressure can be near infinite, or the density can be near infinite, or simply the ...
Mark's user avatar
  • 5,333
1 vote

Steady state approximation for compressible fluid flow (manifolds and other pressure vessels)

Interesting question, but well worth discussion of the confusion of compressible flow equations. At steady state, we will always have the mass flow rate be constant, even with choked flow. The flow ...
Mark's user avatar
  • 5,333
1 vote

Difference between strong, weak and differential forms?

If your course started with an indigestible dose of multi-dimensional calculus without much discussion of how the math relates to the physics (and there are certainly textbooks on computational CFD ...
alephzero's user avatar
  • 12.5k
1 vote

How to model subcritical open channel flow?

What software are you using? If you're just calculating this in a spreadsheet, "Flow in Open Channels" by Subramanya (2009) provides a mathematical treatment of side-weirs which you may find helpful (...
Phil Engler's user avatar
1 vote
Accepted

What limits my Courant number in Implicit Density based Solver?

Analytical stability results for backward-time, centered space (BTCS) discretizations only apply to the first order (linear) hyperbolic partial differential equation. The only reason why they are ...
Paul's user avatar
  • 2,569
1 vote
Accepted

How to force creating a conformal mesh interface between zones in Fluent?

I found the issue addressed in Fluent user guide: Parts are groups or collections of bodies. Parts can include multiple bodies and are then referred to as multibody parts. If your geometry contains ...
Algo's user avatar
  • 2,150
1 vote

Streamlines at the boundary of rotating and stationary domains are malformed

Your stationary domain can't incorporate the time/spatial dependency that the turbine blades should induce in them. Suppose there's a region of high velocity flow that trails a turbine blade by 10 ...
Rick's user avatar
  • 1,335

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