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Posts Tagged ‘Simulation’

Flow Simulation – How to Handle a Vortex Across a Pressure Boundary

Wednesday, April 19th, 2017

What is a “Vortex Across a Pressure Boundary?”

In Flow Simulation, a vortex is a region in the fluid domain which causes a swirl in a region where there is asymmetric drag in the flow field.  The vortex itself is an expected phenomenon which itself is not problematic.  When that vortex is allowed to generate across a theoretical boundary within a CFD analysis that can cause the results to deviate from reality in the immediate vicinity of the boundary or also cause the solver to fail to produce results at all.  For that reason, it is important to note where this is happening in an analysis and take steps to avoid it.

How can this be fixed?

The vortex itself is generating because of the local solid geometry near the pressure boundary of a CFD setup.  If the flow through the boundary is not symmetric, a low-pressure region can generate in front of the boundary allowing fluid to pass the wrong direction through the boundary as intended.  The fix for this is to “build out” the model geometry.  What does this mean? The solid model needs to have more real life geometry added to the setup so the flow field can be allowed to have the vortex and then transition into a unidirectional flow.

Solution 1: Add Geometry

An example of a vortex across a boundary would be directly from the first Flow Simulation tutorial in SOLIDWORKS.

(The tutorials can be found under ‘Help’, ‘SOLIDWORKS Simulation’, ‘Flow Simulation Online Tutorial’ once the Flow Simulation add-in is turned on).  The ball valve, as it is setup in the tutorial, has two lids that are positioned closely to the ball of the valve.  In situations where the ball valve is not set completely open the flow through the valve is forced to be asymmetric as it passes through the pressure outlet.

The asymmetric flow out the pressure boundary allows fluid to backflow through the theoretical pressure boundary and creates the vortex that is seen below. (more…)

SOLIDWORKS 2017 Grouping Components in the Feature Tree

Thursday, December 22nd, 2016

What is a Singularity?

A singularity is a function’s divergence into infinity. Simulation occasionally produces stress (or heat flux) singularities.

How do they occur? Mathematically, the solver uses matrices to represent the elastic field (displacements of the elements). When a highly localized load is applied, the gradients of the displacement vectors begin to diverge, causing the roots of the matrices to go to infinity. For a simplified explanation, see the stress equation below. Stress goes to infinity due to force applied in a very small area.


Where do Singularities occur?

Singularities are usually seen at points, edges, or reentrant corners. Reentrant corners are interior corners, with angles pointing into the part. The high stress concentrations are usually seen near 90 degree corners, but can potentially occur for any angle less than 180 degrees.

Why don’t they occur in real life?

Think of the common case of singularities created on interior corners. In software, that corner is perfectly sharp. In real life, there will always be a slight bend.  Also, the part may deform slightly, or “slip”, and allow the faces of the corner to slide against each other. The slight bend and additional friction allow for a converging stress.
“Adjust your legend’s color settings to grey out above the material’s yield point. This prevents singularities from overshadowing other important stress results!” – Joe Engineer, Know It All, GoEngineer


Olympic Weightlifting Gets Drop Tested with SOLIDWORKS Simulation

Monday, August 15th, 2016

Ever wonder why rubber weights are used in Olympic weightlifting, but iron plates in most gyms?

We did. So, we looked into it.

The World’s greatest athletes demonstrate what it means to push the boundaries of human potential at each Olympic Games. In Olympic weightlifting, for example, new records are being set every year. Much is said about the athletes and how they challenge their limits to achieve new heights, but what about the equipment?

Weightlifting Equipment

  • Has it always been the same?
  • What kind of stress occurs when the bar is dropped?
  • How could pushing the boundaries of design enable athletes to achieve more?

At GoEngineer, these are the kinds of questions that keep us up at night.

Here’s what we found;  changing the material of the weights, changed the sport of weightlifting.

See our Simulation FEA Drop Test

Weightlifting has been an Olympic event since the very first Olympics in Athens in 1896. Back then, the bar and the plates were made out of iron. The rules required athletes to gently return the weights to the ground. This obviously wasn’t possible when an athlete was going for a max effort lift, and would miss.


Batman v Superman – Scientifically Speaking, Who Would Win?

Monday, March 28th, 2016

Batman v Superman – Who will win the battle of the ages?

Batman v Superman: Dawn of Justice hit theatres worldwide.  Previews clearly show Batman holding his own against Superman. As an engineer, I’m a Batman fan at heart. I want to believe that the Caped Crusader will ultimately defeat that Kryptonian. So, let’s take a look at this matchup and use engineering technology, all available to Wayne Enterprises, to devise a plan of attack.

Movie fans and comic geeks will all have their opinion on the battle of the ages. But what does science have to say? Read on…

 (Source: Warner Bros.)

(Source: Warner Bros.)


SOLIDWORKS Simulation – Frequency Analysis of Tensioned Guitar Strings

Monday, February 1st, 2016

SOLIDWORKS Simulation is powerful.  Using this tool, I will demonstrate the correlation between SOLIDWORKS Simulation FEA and the solution of a theoretical equation through the analysis of a guitar string.

In this setup, a single guitar string is restrained on both ends. Restraining the string allows it to reach fundamental frequency, which is 1 half wavelength along the length of the string.

The setup will utilize beam elements for the string as it is long and thin. One end will be fixed in the radial, axial, and circumferential directions, while the other end is fixed in only the radial and circumferential directions. On the free end, a variable force will be applied to observe the change in fundamental frequency on the string.


CFD for the Common Man

Thursday, March 5th, 2015

hot-potato30 years ago, Computational Fluid Dynamics was a topic reserved for PhD analysts or research groups at Universities. Fast forward to 2015 and CFD is accessible on the laptop (or even some tablets) for any engineer with SOLIDWORKS CAD. When we classically think of CFD, applications such as air flow over airplane wings or water flowing through a pipe come to mind. While these quintessential studies were the foundation of the development efforts, we can also study many common everyday scenarios.

Earlier this week I was cooking some fish and vegetables (admittedly both were from a frozen bag). One of my main frustrations with the particular vegetable blend that I used was that the potatoes never come out quite right. Green beans…perfect! Fish fillets…perfect! Potatoes…cold in the middle.

Time to put on my engineering hat! The fish is sliced into thin fillets and the green beans are long and slender. Both of those geometries lend themselves to relatively high surface area to volume ratios when compared to the chunky potatoes. If only there was a way to figure out how long I should leave the baking sheet in the oven without forcing myself to eat fish for the next several weeks.

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