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1answer
624 views

“Transport Phenomena” (Bird, Stewart, Lightfoot) difference between edition 1 and 2 [closed]

What is the difference between Transport Phenomena first edition (1979) and second edition (2002)? Which one do you recommend to be bought, taking into account that I am a student and that the first ...
3
votes
1answer
259 views

Which type of Turbine (Pelton, Francis, etc.) is most suitable to be driven by high velocity forced-air jet?

Which type of turbine (Pelton, Kaplan, Francis, etc.) would be suitable and deliver the best efficiency when driven by a high velocity forced air jet of 125-200 mph through a nozzle of 2-2.5 inches ...
5
votes
1answer
444 views

How could we possibly harness the energy from the Earth's negative charge?

I've been reading the Feynman lectures, and in this lecture about lightning, he describes how the Earth is negatively charged, and how there is thus an electric field of about $100\ \tfrac{\text{V}}{\...
6
votes
5answers
299 views

Can redundancy be used instead of periodic calibration?

A lot of production equipment requires periodic calibration as part the documentation that the equipment is under control. The companies selling the equipment knows this and sometimes lowers the price ...
12
votes
4answers
4k views

How thick is it reasonable for the walls of a steel gas pipeline to be?

The TurkStream project site claims the gas pipeline will use pipes made from 39 millimeters of high-quality carbon manganese steel with additional plastic coatings on both sides. Yes, they claim 39 ...
10
votes
1answer
453 views

Does weathering steel corrode the same as carbon steel when it doesn't develop a protective patina?

Weathering steel is supposed to form a protective patina when exposed to wetting and drying cycles. This protective patina prevents more corrosion from occurring. This is what differentiates it from ...
6
votes
4answers
822 views

How can I calculate the rate of power consumption of a solar car along a known route with changes in elevation?

I am working on designing and creating a solar powered car for the Solar Car Challenge. The car will have to race from Dallas, TX to Minneapolis, MN in 5 days (~5 hours of driving a day) along back ...
7
votes
1answer
240 views

How do I select an appropriate turbulence model?

Turbulent flow involves extremely small scale fluctuations which are usually too small to resolve by using the Navier-Stokes equations directly. To overcome this, we model each transient variable $\...
2
votes
0answers
140 views

Problem in an axial turbine

I am simulating an known as , using CFX as a solver. This turbine have 8 blades((360/8)=45 deg=pitch angle). Due to the circumferential symmetry, only one eight of the annulus has been computed, ...
1
vote
1answer
140 views

From strain to displacement in 3d

I got a question thats been bugging me for a while: Say that you're given a straight square beam (say one meter long), and you attach three strain gauges on each face. One at 0 degrees, one at 45 ...
3
votes
2answers
160 views

Virtual Work - Determining Relationships in deflections

I'm having problems understanding the worked answer for this problem: Here's part of the worked answer: I don't understand why $\delta_C = \dfrac{4}{9} \delta_A$ . Can you please explain that part ...
1
vote
1answer
60 views

Uniform values from different MEMS 3-axis accelerometers

I have to find a solution to uniform values on 3-axis accelerometers on different android devices. I mean, a device with a specific accelerometer, under the same acceleration, give me values for 3 ...
5
votes
3answers
501 views

Center of Pressure Line from Barefoot Scan (EMED)

I have raw data obtained from EMED barefoot scan containing a matrix of pressure sensors over about 70 frames. This totals 70 matrices that record a snapshot of the pressure over the duration of a ...
1
vote
2answers
130 views

Can somebody explain how this equation(based on conservation of mass of a fluid) came about?

This is taken from Versteeg and Malalasekhara CFD book. δx, δy, and δz are given as the dimensions of the sides of the fluid element under consideration along the three axes respectively. On the ...
5
votes
2answers
116 views

What could be the downsides of leaving twist-off bolt splines in the interior of exterior columns?

I have a project where the contractor is using ASTM F1852 Tension Control (twist-off) bolts. The project is outdoors and uses weathering steel and weathering fasteners. The main members are hollow ...
5
votes
1answer
931 views

Determine the range of values for a PI controller

This is a basic control theory question, since Control Theory is a part of applied mathematics but also of engineering I was unsure whether to ask this here. The question says: Given the transfer ...
5
votes
2answers
2k views

ANSYS Workbench/Mechanical: Automatically export chart?

I'm running a simple tensile test simulation for a single element. Under Results I made a Chart object with Stress vs Strain, which can be manually exported to a csv file by right clicking on the ...
8
votes
2answers
947 views

Why are creeks sometimes piped underground in urban areas?

I live in Melbourne, Australia and a lot of the creeks here have been diverted through underground storm water pipes. I guessed that this is because land is highly sought after for development, and a ...
5
votes
1answer
544 views

What is a non-equilibrium boundary layer?

I studied a manual of Ansys CFX about turbulence models and I came across the term "non equilibrium boundary layer". What does this term mean?
2
votes
0answers
913 views

Flow velocity in exhaust chimney - typical design value

I'm looking at a project where stationary CHP engines will be replaced, leaving as much of the infrastructure in place as possible. Current exhaust velocity in the chimney is ~42m/s and it will be a ...
4
votes
1answer
121 views

How can I get a quick 2B shine on grade 316 stainless steel?

I have a stainless steel (316) 2B finish strip. I tried buffing the material for a shiny surface but it takes lot of time to finish my production. So, I want to know if there is any chemical ...
4
votes
1answer
63 views

How does non-electrical ATEX apply to springs?

This question relates to the ATEX directive, which is the European regulation governing the design of products to be used in explosive atmospheres. In particular, I am asking about the part relating ...
4
votes
3answers
294 views

What is this kind of X-Y motorized system?

I'm wondering what the technical name is for this kind of stepper-motorized arrangement (a positioning system? an XY table?)? What is it typically used for? It appears to have two steppers as ...
3
votes
1answer
39 views

Analog addressing flat panel display

Cathode ray tubes (CRT) are analog addressing displays because you can light a point on its surface applying a continuous electric or magnetic field to deflect electrons beam. Virtually, there is no ...
4
votes
2answers
1k views

Arranging members within a truss efficiently

A wide variety of trusses exist for bridges and roofs. There are many different permutations when it comes to arranging the internal truss members. Depending on the direction, a diagonal member may be ...
4
votes
2answers
233 views

Measuring the distance to an object with RF resonance

Assume I put an RF antenna in front of an object (typically the face of someone sitting in a chair, so able to move about +/- 10cm in all directions) at a typical distance of 1m. If I consider the ...
5
votes
0answers
107 views

Schematic Reading - Fluid Control Limit Switch Question

Does limit switch LS1 remain pressed on until the piston moves to LS2?
3
votes
1answer
1k views

Increase static pressure

I have an application (a tube with parts in it) which needs a certain static pressure in it in order to contain a sustainable air flow. Unfortunately the fan I wanted to use in a push-configuration is ...
1
vote
1answer
603 views

Frame/truss problem with sliding joint

I'm supposed to be finding the reaction forces first but from the FBD of the entire truss where am I supposed to start. If I take the moment at A then I get 3 unknowns at Bx Dy and Dx. If I get the ...
1
vote
1answer
1k views

Loaded Truss problem

Hi, I'm having some problems with this truss question that I have in my homework. So far this is my solutions. I worked out my solutions to the reaction forces but don't know if they're correct. The ...
0
votes
3answers
141 views

Crushing drink cans

I have a 15 pound weight that I use to crush 8.4 oz red bull cans. A metal barbell with a handle and 2 ends. Not 100% flat ends, but close to flat. About 12 inches from end to end. I hold the barbell ...
11
votes
3answers
38k views

How to determine the characteristic length in reynolds number calculations in general?

I understand that the reynolds number is given by the expression $Re=\frac{\rho v L}{\mu}$, where $\rho$ is the density, $v$ is the fluid velocity and $\mu$ is the dynamic viscosity. For any given ...
5
votes
1answer
481 views

What is the difference between being UL recognized and being UL listed?

A product can be UL recognized or UL listed. I understand that there is some difference between these two things, but I have never had a full and clear explanation of the difference. What is, in fact, ...
0
votes
1answer
64 views

Find optimal configuration for Stirling Engine

I'm trying to figure out the theoretical calculations for a Stirling Engine system so I can determine optimal piston size, optimal piston displacement and number of pistons. I want to calculate which ...
3
votes
0answers
129 views

Is there a way to obtain a circuit of some sort given a Nyquist plot?

I have some transfer functions and I was wondering if it would be possible to approximate this to an electric circuit equivalent. For example, given the Nyquist plot below, is it acceptable to ...
5
votes
1answer
141 views

How do I interpret the curing pressure of a composite from this data sheet?

A question asked about the necessary curing pressures for a composite resin in the autoclave. Looking through the corresponding datasheet (HexPly F155), I'm confused: Cure Procedure Apply ...
6
votes
2answers
712 views

How can I finish a round hole so it has 90 degree corners (flat bottom)?

I have a 10 mm depth x 5 cm length 99% Tungsten rod. How can I machine the described hole so that instead of having a bevel from the tip of the main drill-hole bit, it has a perfect 90 degree corner ...
1
vote
0answers
150 views

How do I determine plate thickness and anchor size for a 10-ton span supported by synthetic rope?

I am supporting 25,448 pounds over a series of cables, spaced 20' apart, over a span of approximately 424', left to right. The load is mostly in an area of the middle 10' of the span. I am using ...
6
votes
1answer
52 views

If my electronics are outdoors in a ventillated NEMA 4 enclosure, should I conformal coat my circuit boards?

I'm considering putting a circuit board in a ventilated NEMA 4 enclosure outdoors. I'm a little concerned about humidity and condensation inside the enclosure. Do I need to conformal coat my circuit ...
3
votes
1answer
124 views

How did Al-jazary's “castle clock” work?

My question is what are the ideas behind the complicated historical water clocks. According to wikipedia, modern versions of the historical water clock rely on the principle of the syphon. So I ask ...
3
votes
1answer
453 views

Gas cleaning in activated carbon filters - How much moisture is needed and why?

Biogas and sewage (typically around 60% CH4, rest CO2) gas is typically treated in activated carbon (ac) filters to remove H2S and siloxanes. The ac filters need a small amount of oxygen (>0,4%) to ...
1
vote
1answer
881 views

What screw for 2.0 mm plastic hole in housing

I'm thinking about using the Bopla UM 32009 housing for my product. It has little standoffs for attaching PCBs. These standoffs are made of plastic, and seem to be drilled (or molded?) to a diameter ...
4
votes
1answer
347 views

What is the accuracy of direct metal laser sintering (DMLS)?

They've printed jet engines with it that work after polishing. So how is the accuracy measured and how accurate is the DMLS process? I can't find the required info anywhere.
5
votes
1answer
127 views

What's the smallest pin-like hole I can machine into a piece of tungsten using a metal lathe and common carbide tools?

I am going to machine something out of a small 40mm long x 8mm diam tungsten rod. The majority will be hollowed out using a larger bit, but at the very tip, I need a small hole, the smaller the ...
6
votes
3answers
6k views

Is inviscid flow necessarily turbulent?

The Reynolds Number is defined as $Re = \frac{\rho v L}{\mu}$, where $\rho$ is the density, $v$ is the fluid velocity, $L$ is the characteristic length, and $\mu$ is the dynamic viscosity. By ...
0
votes
2answers
206 views

How to move a thin metal piece with a tiny string or anything else?

Recently I was experimenting with a metal piece, and I came across a challenge. A small piece of thin copper metal (5cm x 3cm x 0.2 cm) has to be pushed forward and to be rotated. The problem is how ...
5
votes
1answer
798 views

How do I calculate rolling resistance for tire on pavement?

First condition assuming perfect rolling, no slip, from what I understand is that the rolling resistance coefficient can be calculated as the displacement arm of the normal force the tire "feels", in ...
7
votes
0answers
474 views

BER peroformance of MPSK and MQAM in Rayleigh fading channel

I have a question regarding bit error rate (BER) performance over the Rayleigh channel. I observed BER performance over the AWGN channel using Simulink in MATLAB. I used to change the "SNR" parameter ...
4
votes
1answer
4k views

Difference between continuous wave laser and a pulsed laser

I understand the difference between the two in terms of how they function; one will release all of it's energy in small pulses with the other creates a constant stream of radiation. My question is ...
10
votes
2answers
558 views

Differential equations of a (simplified) loading bridge

I am having trouble to calculate the differential equations of a simplified loading bridge. The system is build as shown in the picture below (just a sketch): If I use the Newton approach, I am ...

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