37 votes

From an engineering point of view what are the downsides of a too accurate model?

Beware of overfitting. A more accurate model of gathered data from a system may not be a better predictor of future behavior of a system. The above image shows two models of some data. The linear ...
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  • 479
26 votes

From an engineering point of view what are the downsides of a too accurate model?

The most obvious downside is cost, all engineering projects have a finite budget and spending more money than you need to is clearly a bad thing not to mention wasting time. There can also be more ...
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24 votes
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How do engineers really use numerical simulation?

I have written mostly about CFD in this answer, however same points should also work for FEA or other simulation techniques. CFD is mostly used for design optimization and parametric study of the ...
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13 votes

How do engineers really use numerical simulation?

To summarize the other answers: An engineer needs to know qualitatively how the simulation will go, but he still needs to run the simulation to get the quantitative answer. Also, simulation allows ...
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13 votes

From an engineering point of view what are the downsides of a too accurate model?

There are a few reasons. From a purely pragmatic perspective, it's due to time constraints. The requisite time to solve a model increases far, far faster than the level of precision, and whichever ...
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12 votes
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Which turbulence models are suitable for CFD analysis on a streamlined vehicle body?

The turbulence model can make a big difference in your simulation. There are many turbulence models around. It becomes a tough job to select one out of them. There is no perfect turbulence model. It ...
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9 votes

Meshing of complex geometrical domains

There are a number of techniques for meshing complex domains for Finite Element Analysis. They generally fall into two categories: Structured vs. Unstructured. For structured meshes, basically the ...
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  • 493
9 votes

How do engineers really use numerical simulation?

Engineers should have a general idea of the expected result (Balpark values, expected behaviour)when using a complicated computer model. Most of the time these conclusions are based on a (much) ...
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8 votes
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Sending out a 12d Civil Design Model

Before I start, let me disclose that I don't know a lot about the details of infrastructure projects or your file format, but I think the general considerations are fairly universal. There are a ...
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  • 4,501
8 votes

How do engineers really use numerical simulation?

As my Fluids lecturer said many years ago, “if the mathematics doesn't agree with reality the mathematics is wrong”. You can easily substitute the words model, theory or simulation for the word ...
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7 votes

Can two different modeling programs be used to confirm the results of each other?

Yes, getting a second opinion can be useful. This is done routinely in weather forecasting where exact solutions are unknown, and there is some judgement about how to apply various factors. There ...
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6 votes

Can two different modeling programs be used to confirm the results of each other?

I write this from the perspective of an engineer who develops simulation software. I think the practice described is bad, and I recommend you do not use two different softwares to "confirm" the ...
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6 votes

Is a distributed load in two parts equal to a full distributed load?

Splitting a uniform load into separate pieces that are still continuous will have no effect. This is frequently done. As far as your question about bending in HE and EB, there shouldn't be any ...
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6 votes

Meshing of complex geometrical domains

While the other guys explained the theoretical framework behind meshing, the practice is markedly different and it is not at all automatic in industries where quality of mesh is of utmost importance ...
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6 votes

Differential equations of a (simplified) loading bridge

Kinematics and dynamics Those are the steps to solve problems of this nature. Analize the kinematics of the system. $\hspace{5.em}$ $_{o}\vec{r}_{OP}$ = $_{o}\vec{r}_{OR}$ + $_{o}\vec{r}_{RP}$ $\...
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6 votes
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How do you model a real-life truss in structural analysis software?

The most common way to model this structure is as follows (ignore the fact that the proportions are a bit off): So, all of the diagonals are pinned-pinned. You'll notice in the schematic, however, ...
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6 votes

From an engineering point of view what are the downsides of a too accurate model?

An extremely accurate model may require a prohibitive amount of input data. It might be possible to generate an excellent model of weather systems, for example, by taking as input the position and ...
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5 votes

How do engineers really use numerical simulation?

In my particular field (buried culvert design), we run finite element analyses constantly. We almost never change a design based on the results; we know going in (from a variety of factors, mostly ...
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5 votes
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Modelling splashing water in FEA

This may be only a partial answer since I don't have any idea what to do for the Young's modulus of the fluid. Consider the paper Dynamic Pressures on Accelerated Fluid Containers by G. W. Housner. ...
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5 votes
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Differential equations of a (simplified) loading bridge

My guess is that you probably need another differential equation for the angular movement, that will involve the inertia, such as: $$m_G l^2 \ddot{\varphi} = m_G g l \sin(\varphi)$$ which yields: $$...
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5 votes

Adding a lubricant to an already lubricious material, how is CoF affected?

You can't calculate friction coefficients this way. At the atomic-scale level, the friction coefficient depends on the interactions of the two materials across the interface. If you measure the ...
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5 votes

From an engineering point of view what are the downsides of a too accurate model?

"Too accurate" is not monotonic. It can actually create an illusion of fidelity which makes you think it's worth pumping more money into the simulation. This becomes very important when you're ...
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4 votes

Can two different modeling programs be used to confirm the results of each other?

I think this is a good practice overall. By using two different softwares, you may be able two avoid two kind of errors: 1) errors that come from an inaccurate software (which should not be ...
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4 votes
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Is a distributed load in two parts equal to a full distributed load?

I would expect the modeling as a single load to be accurate. Force per linear area is the same expressed either way. You could look at a linear load on a single beam and just add more points of ...
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4 votes
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connectedness between the output voltage and input voltage

You can write two ODEs describing the relationship, and that would be in the time-domain. Alternatively you could describe things in the frequency domain and get the relationship as a transfer ...
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  • 1,876
4 votes

How to define Knurl on drawing?

It looks to me like your guess was pretty good. The required information is only the type of knurl, the extents of the knurl, and the pitch. It is conventional to show the representative pattern, but ...
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4 votes

How to define Knurl on drawing?

The (European) standard for knurls is DIN 82. The standard includes a proposed drawing representation as well. Its intention is to describe hand gripping aid knurls. As Ethan48 says, for fitting you ...
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4 votes

How I can compute cutting processes with continuum mechanics?

Real-world engineering example To my knowledge there are no simple analytical methods of determining whether an object such as a sword can cut cleanly through any arbitrary object. In manufacturing ...
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4 votes
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polar moment of inertia for compound shape

Without looking up all the formula's for you, the approach to this problem is rather simple. Find the polar moment of a solid cylinder, and subtract off the polar moment of the holes. For the off ...
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3 votes

Is a distributed load in two parts equal to a full distributed load?

Adding just a slight notion: Your experience would always expect the beam HE to buckle, because it is a Eulerian buckling beam (don't know if it's also called like this in English). The numeric only ...
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