Questions tagged [modeling]
Use this tag for questions about numerical or analytical modeling and simulation of engineered systems.
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Example of real-life problem solved with numerical methods? [closed]
I hope this is a suitable question to ask here.
Well, I'm taking Numerical Methods this semester (also called 'Numerical Analysis' in some places).
The term-assignment is to find a real-life problem ...
2
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1answer
47 views
Modelling gas desorption from a still solution (e.g. a beer)
The common way to model or estimate gas (e.g. CO2) desorption rate from a liquid solution is by using an equation similar to this one
$J_{CO_2} = -k_L a(H·C^G_{CO_2} - C^L_{CO_2})$
where $J_{CO_2}$ ...
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3answers
71 views
Git, Mercurial, others — what's the best system for an engineering team new to version control?
I recently started working with a new team doing detailed energy modeling for all flavors of building projects -- commercial, industrial, residential, new construction, renovations, additions. As the ...
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0answers
31 views
How to join two beams rigidly?
Hi I am making a beam model using Abaqus. There are two beams created. I wanted to join two beams rigidly in the connection to transfer moments between beams. However, I do not know what connector or ...
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2answers
30 views
How do you read a blower/compressor curve with multi-curves for inlet guide vanes?
I am trying to apply an existing blower curve in a hydraulic model for a single stage blower with variable inlet diffuser vanes. The variety of curves shown on the plot does not seem to make sense to ...
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0answers
15 views
Should I use a regular curve fitting tool or system identification to calibrate/model a gyroscope to a reference?
I want to create a model that describes how well a gyroscope can approximate the angular velocity that I apply to it. Since it's never really possible to obtain the exact angular velocity, it is based ...
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1answer
39 views
How to make datum planes on a cone in Creo?
I am trying to make this
I was able to make the base feature but I am facing problems with the secondary features. So could anyone shed some light on how to make the datum planes on cones.
I made ...
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1answer
46 views
How does the superposition principle relate to Bernoulli-Euler and Timoshenko beam theory? [closed]
I have a shaft with a bearing in each end, and a large eccentric mass covering the entire "free length" of the shaft.
The attachment of the eccentric mass is done using heat shrinking.
Without ...
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0answers
25 views
Bad triangular-shell elements in Abaqus?
Abaqus 6.14
I have a 2D shell mesh reconstructed from a *.ply file. When I verify the mesh I get 55% bad elements (CPS3).
So I get a list of all the bad elements & reconstruct the mesh again ...
1
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1answer
30 views
Predicting frequencies, decays, levels, and phases of modes of a circular membrane (drum head)?
I have been working on some acoustic synthesis software for modelling several acoustic instruments. I am using the principle of modal synthesis, where every mode of vibration is individually ...
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1answer
30 views
Modeling the stiffness of a membrane
I'm trying to model, in MATLAB, a membrane in 2D which has an initial triangle-like shape.
This membrane has pressure acting on it from the inside. There are also some pulling forces in random ...
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0answers
14 views
How to export my model as Solid model IGES Type 186 on Rhino?
I'm not able to find that option while exporting. I need to export this to ANSYS where the other available IGES formats come as only surface models.
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0answers
21 views
False turbulence in laminar flow with k-omega SST
I have a pipe with a sudden expansion from 0.25 mm to 1 mm. Fully developed flow is at the inlet and a reynolds number of 500.
I use k-omega SST turbulence model because laminar simulation hasn't ...
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1answer
50 views
What is the advantage of successive linearization?
In this link, two methods have been referred for linearization.
1- offline linearization
2- online linearization
However, I do not understand what is the role of "successive linearization" in the ...
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2answers
28 views
How to estimate the time cost of interrupting a task and picking it up again later
In terms of personal productivity (single machine scheduling) when a task is interrupted before being done in order to switch to a different task, it incurres a 'tear down' time cost - putting tools, ...
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0answers
25 views
How to run response spectrum for members with compression only spring in MIDAS
When running a structural model supported on footings with compression only springs, I encountered tension reaction forces in the springs. This occurs when running seismic load case using response ...
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1answer
30 views
Thermal Modeling
I have an electronic assembly and part of what it does is to measure and report temperature. The electronics are housed is a plastic enclosure, and there is a small fan blowing out of the enclosure. ...
1
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1answer
31 views
simplified acceleration and max speed calculations for a game? [closed]
Are there any simplified formulas that could be used to generate plausible airplane, spaceplane/SSTO, and spacecraft performance specs for a game given some basic vehicle and contextual attributes? By ...
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1answer
21 views
Can anyone briefly explain each of the values output by HEC-RAS please
I am looking at a Flood Risk Assessment that uses HEC-RAS to model the predicted levels of flooding on a piece of land. As shown in the attached image, the report lists a number of variables with ...
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0answers
11 views
How to find the maximum misalignment from vibration?
Consider the system in the (drawn in Paint) image. Assume that there is an input acceleration at the ground defined by a PSD. This acceleration can be in any axis. Points A and B are initially aligned ...
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0answers
22 views
autocorrelation function of mechanical displacement
I was wondering if there any work in the literature that has been done on the form of the autocorrelation function of mechanical displacement of an object.
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0answers
66 views
Questions regarding Cornering Stiffness for RC Car
I am a bachelor's level student tasked with modeling the vehicle dynamics of an RC Car that will be made to drive autonomously. I lack prior experience or particularly specific education with vehicle ...
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2answers
72 views
Failure of N.R.T.L method to model Phenol / Methylcyclohexane / Toluene system in AspenPlus. Why?
I have an extractive distillation column set up in AspenPlus. Methylcyclohexane (MCH) is expected to come out from the top (in the distillate stream) and the bottoms stream is mostly Toluene/Phenol, ...
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1answer
81 views
Energy consumption of a boiler
I have a question that maybe will be very easy for you.
I am working on a district heating model using Dymola, and now I have to incorporate a boiler into my model, such as this one.
I was asked to ...
5
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1answer
80 views
Would a partial space elevator work? [closed]
Background
The normal space elevator (that reaches from the Earth's surface to a counterweight beyond geostationary) needs a material that's strength/weight ratio is better than any material we have ...
0
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1answer
38 views
How to determine the degrees of freedom for ball and beam system such as shown in pic below
Since, motion of the ball on the beam depends on the beam angle alpha, shouldn't this system have a single degree of freedom?
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11answers
8k views
From an engineering point of view what are the downsides of a too accurate model?
I was wondering, from an engineering point of view, for what reasons can too much accuracy in modeling be detrimental?
From a scientific point of view it seems like it's almost always a benefit, ...
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1answer
54 views
What is an unstructured mathematical model?
I want to model a chemical process. I was searching in the literature to find similar works. In some of papers they say that "we proposed an unstructured model". What does it mean? What is the ...
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0answers
38 views
1D heat equation for conduction with convective bounary conditions
I have a question related to the 1D heat equation.
The equation I have is more complicated with additional terms.
Capital T is temperature and is a function of x and t so written as T(x, t) where ...
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3answers
83 views
What program to implement mathematical models? [closed]
I am an engineering student and recently came upon some articles that provide numerical models that relate electromagnetic fields and temperature. I want to test out these numerical models but am ...
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0answers
19 views
Linear Guidance law into X-Y axis
Im currently writing a model for a guidance law named Maintaining Guidance law.
The law looks as following: $$ a_{M} = [K_1,K_2]*[\dot{\lambda_T} ,\dot{\lambda_D}]'$$
Since im using a linear model I ...
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0answers
45 views
Help needed with designing a wind turbine (VAWT)
So I have a design for a wind turbine to use in my garden. It is a fairly average darrieus wind turbine design. The wind speed in my garden maxes at about 30mph and constantly changes direction.
My ...
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1answer
213 views
polar moment of inertia for compound shape
I have a shape that I'd like to calculate the polar moment of inertia for:
the diameter is 600mm; the hexagon in the middle sides are 70mm each; the holes around the hexagon are 130mm from the center ...
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1answer
110 views
Maximum torsion shear stress in cylinder
I am trying to figure out am I doing this calculation correctly.
To get the maximum shear stress for a solid cylindrical pipe I need two formulas:
Moment of inertia = pi/2*r^4
Not sure what this ...
0
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2answers
67 views
moment of inertia forces and torque
I did some calculations to find out the moment of inertia and physical qualities of some metal.
I am using typical medium carbon steel.
I'll use a density of 7.8 g/m^3 until I get better numbers.
...
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2answers
71 views
Looking for program and file format for CNC Milling
I am creating subwoofer boxes out of MDF or Baltic Birch. My local makerspace has a CNC machine. I am going to make all of the cuts with it.
What software is generally used or will work to get a ...
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0answers
25 views
Holonomic constraint forces using Lagrange multipliers
Consider a multibody robotic system with Lagrangian $$ L =\frac{1}{2} \dot{q}^{T}M\dot{q} - V $$ and equations of motion of the form
$$M(q)\ddot{q}+C(q,\dot{q})\dot{q}+A^{T}(q)\lambda+N(q)=0 $$
where ...
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1answer
92 views
How to use failure criteria in isotropic material (NASTRAN)
I'm quite new in NASTRAN enviroment, and I am wondering how to use failure criteria which I can define when creating my isotropic MAT1 material for 1D elements (like CBEAM).
From the Quick Reference ...
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2answers
142 views
Specification of linear speed dampers
I'm looking at linear compression dampers and finding them most commonly specified only with a "Max Force" – e.g., 270 lbs.
However, since the damping mechanism is provided by hydraulic or pneumatic ...
3
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1answer
96 views
Is it possible to apply different boundary conditions on the same model for different load cases?
Instead of creating multiple bridge models with different boundary conditions for differential settlement, and combining the forces output manually in Excel, is it possible to specify different ...
3
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1answer
98 views
Should sum of all joint reactions be zero when nodal displacement is applied?
I created a structural model of a laced strut using plate elements. To study second order effects of bow imperfection, I applied a joint displacement of 20 mm in a SAP 2000 v18 model. When the ...
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0answers
40 views
Best software for 3D modeling and simulation semiconductors? [closed]
Need to design 3D model of photodiode and calculate it (interaction light with semiconductor). What software product would be better for this objective and why?
Important criteria:
Big library ...
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1answer
204 views
How to model a planetary gear system with transformation matrices?
I need to model the planetary gear-train with transformation matrices of 1 sun and 2 planets system, with no ring and an "arm" or carrier holding the gears ,like in the second picture. I already have ...
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1answer
38 views
How I can compute cutting processes with continuum mechanics?
In YouTube I have seen various videos where someone cut with a sword into hard objects and has cut that into pieces. For example:
https://www.youtube.com/watch?v=EVCWGwvctt4
Given the mass, the ...
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2answers
162 views
Modelling a DC motor
I am modellign some examples using the modelling language Modelica. Unfortunately, I am not an electrical engineer, so it is hard to understand the physical behavior of the following example (DC motor)...
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1answer
51 views
Using a controller for a simple heating system
I am new to control modeling. Given the following problem: I want to control the heating of a house. Therefore, a top unit should be switched on (nominal load, no ramp up) as soon as the production of ...
3
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1answer
220 views
Two dimensional plasticity with radial return
Note - This is a duplicate of the question I asked over on Physics which hasn't received any attention.
What is the proper method to scale deviatoric stresses back to the yield surface in plane ...
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2answers
75 views
Need help with interpreting units of kinetics data in a scientific paper
I need help with interpreting the kinetics of a scientific paper: https://www.researchgate.net/publication/...
0
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1answer
68 views
What do these sigma subscripts represent?
Axial strength for balsa wood at different densities
What I don't understand are the subscripts under the sigmas (strenghths.)
How do I know where the compression (crushing) and tensile strengths are?...
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0answers
76 views
What is the best way to model a beam and slab bridge? [closed]
I notice bridges designed by bridge engineers in my company invariably uses two models. One model for seismic load case and another for other load cases. I was told that some bridge elements, such as ...
