# Search results

1. ### When are the Navier Stokes equations invalid?

To analyze compressible flow I would need to rewrite the NS equations or just add the energy equation to the mix? The difference that I see is that, in compressible flow, the density also changes and so becomes a variable, and I would need another equation to describe the flow.
2. ### When are the Navier Stokes equations invalid?

I've read that one of the assumptions is that the NS equations are for a incompressible flow. So, for dealing with compressible flow problems, the NS equations cannot be applied?
3. ### When are the Navier Stokes equations invalid?

I'm studying the Navier Stokes equations right now, and I've heard that those set of equations are invalid in some situations (like almost any mathematical formulation for a physics problem). I would like to know in which situations I cannot apply the NS equations, and what is the common...
4. ### Mechanical vibrations + Aerodynamics?

I must have expressed myself poorly. Those are not the only graduate options, but the ones that I find relevant for what I want to specialize in, and those are the Aerodynamics, Propulsion and Energy group and the Solid Mechanics and Structures group. There are groups in materials engineering...
5. ### Mechanical vibrations + Aerodynamics?

Aeroacoustics looks like a very interesting topic. I've thought about that, too. For a MS, I can choose between solid mechanics and aerodynamics and energy. Aeroelasticity looks like a very interesting path to follow, but I don't want to get stuck in the solids side if I ever decide to switch...
6. ### Mechanical vibrations + Aerodynamics?

Good to know! As a student, I know very little about the work environment in engineering companies. Had the idea that most engineers had a specific niche and attended only to that. Where I study, aeroelasticity is usually taught by the solid mechanics research group, that's where I've got the...
7. ### Mechanical vibrations + Aerodynamics?

I'm probably going to pursue a specialty within aerodynamics, so I wanted to know if aerodynamicists could work directly with that. Looks interesting. One doubt I've always had: how "stuck" do you get within a field in industry? I mean, if one is a aerodynamicist working with flutter analysis...
8. ### Mechanical vibrations + Aerodynamics?

My professor used airplane flutter as an example in one of his last classes, and it looked like a very interesting topic. Engineers working with that are usually vibration engineers or aerodynamicists?
9. ### Mechanical vibrations + Aerodynamics?

I'm now taking classes on mechanical vibrations and fluid dynamics, and those are two fields that are very interesting to me. I've always liked the subject of aerodynamics, but now I'm really liking to study mechanical vibrations, very interesting field of study. I'm looking for some specialty...
10. ### Strength of materials vs Theory of Elasticity

Yes, I know that. My question is: how is strength of materials applied to those components today. We learn how to calculate stress on simples elements: rods, beams, shafts... A gear is a complicated thing, and I have no idea how to model something like that using strength of materials. And my...
11. ### Strength of materials vs Theory of Elasticity

In strength of materials, we learn how to calculate stress and strain in some basic structures: shafts for torsion, beams for bending... Also, we have the theory of thin shells to calculate stress on structures like pressure vessels and airplane fuselages, or maybe a ship hull. The way I see...
12. ### Strength of materials vs Theory of Elasticity

Thank your for the answer. In strength of materials, we learn how to deal with some structural components like beams, rods, etc, and how to calculate stress and strain in them. We know that we simplify some real life structures so that they can fit in the models that we have and apply the...
13. ### Strength of materials vs Theory of Elasticity

In mechanical engineering we have various courses in strenght of materials, and I've noticed that graduate students learn the Theory of Elasticity. I've researched a little bit about it, and I know that the Theory of Elasticity is more general than strenght of materials. But I have some doubts...
14. ### Shaft in torsion?

Okay. So when I treat one end as fixed is just a way of simplifying things. Actually, it's not really fixed, only in relation to the other end.
15. ### Shaft in torsion?

Suppose I have a shaft supported by a pair of bearings, one at each end, and there's a motor connected to the shaft. When we start the motor, the shaft will rotate with some angular velocity. Why would the shaft twist then, if it is free to rotate because of the bearings?
16. ### Shaft in torsion?

I have some conceptual doubts about shafts subjected to torsion. When studying Strenght of Materials, to find stress and strain in power transmission shafts, we consider that one of the ends of the shaft is fixed, with all degrees of freedom restricted, and the other one is receiving torque. I'm...
17. ### The Boundary Element Method?

Well, but probably BEM still has advantage on some fields, right? My professor's research in university is pretty much focused only on BEM.
18. ### The Boundary Element Method?

Hello! I'm starting a project with one of my professors at college whose subject is the Boundary Element Method. I've studied a little bit of Finite Element Method, but BEM is new to me. This project will envolve a lot of programming in Python and Matlab. I would like to know how does BEM...
19. ### Calculations for weight-lifting motor...

Probably something like 2cm/s. The speed is not a critical issue in the project
20. ### Calculations for weight-lifting motor...

I've thought about designing my own gear train, but that would increase the cost too much.
21. ### Calculations for weight-lifting motor...

I will certainly give a look at that. Thanks! Indeed, I've found some 12 V motors with gearbox, but most of them don't have the torque that I need. Most of these are small DC motors for robotics and automation. The project I'm building will be exposed to environmental effects (sun, rain) so I...
22. ### Calculations for weight-lifting motor...

The project I'm building involves a 12 V electric motor connected to a spindle lifting a 20kg weight. The radius of the spindle is 2cm, so the torque applied by the weight is 0,02m*20kg*9,8m/s^2, which gives me 3,92N*m. So, my 12 V motor needs to deliver 3,92N*m just to keep the weight steady...
23. ### Internal Forces Diagram: how to do this one?

Okay, so let's consider figure 2. When I draw shear and moment diagrams, I plot internal forces in function of x - where x is the distance related to the origin, let's say, point A. But the structure has joints in other directions - y direction, for instance. So, in this case, I have to draw six...
24. ### Internal Forces Diagram: how to do this one?

I'm wondering how should I do analysis on those problems below: Figure 1: Figure 2: I mean, my professor, while doing an example very similar to Figure 2, he didn't do an imaginary cut in the region BD to find internal forces there, and the internal forces diagram that he drew only contained...
25. ### Abaqus FEA: What do e11, e22 and e33 stand for?

I'm new to Abaqus and FEA in general, but my professor asked the class to do a simple analysis on a beam using Abaqus, just to introduce us into FEA methods. I've managed to do almost everything he asked for, but I'm confused about some notations when I get the results. I understand that s11...
26. ### Software for learning structural analysis and FEM?

I'm in the third semester of mechanical engineering and I'm taking classes on engineering statics right now. Our professor said the he will give us a preview of finite element methods at the end of the semester. Which softwares would you recommend for learning basic structural analysis? I mean...