Wind Definition and 829 Threads

Okay, so the scenario is a passenger car, traveling on the highway. As a general rule, I say that increased weight (mass) will have a beneficial effect on MPG (IF tire pressure is increased so that rolling resistance is reduced to compensate for the increased weight), ONCE the vehicle is up to...

What's the difference between cold moving air and hot moving air? For instance, suppose you put two fans, of the same type, each in one room. One room is cold because the walls are covered in ice and one room is hot because due to the effect of heaters. Turn both fans on and the air flow, the...

With large wind turbines which have AC generators why do they convert from AC to DC and then back to AC before connecting to the grid, why not just connect straight from generator to the grid without converting? Very confused please can someone explain!

Homework Statement I have an example problem I would like to solve and unsure how to graphically set up the problem. I would like to derive the answer by the component method of deriving vectors instead of law of sines/cosines. An airplane is trying to keep on a due west course towards an...

If the hood of my at rest car is 106 degrees and I drive at 55 MPH, how much is the hood temparature reduced by the wind so created?

So awhile ago I was thinking about wind. Sometimes wind is hot but when I think of wind I usually think of cold wind. Wind seems to be fast moving particles and I know based on the kinetics theory of gases KE = \frac{1}{2}mv^2 = \frac{3}{2}kT Maybe, I'm making a wrong assumption but...

I just returned from a tenting trip. In a tent, one hears the sounds of night more plainly. I was struck by the fact that, try as I might, I can not distinguish the sounds of wind from those of running water. Specifically, Moderate winds (15-30 kt) in the forest. Moderate winds (15-30...

If I put vents on the hood of my car and drove at 60mph what kind of psi could be achieved? I don't care about what kind of technique is used just curious about what kind psi could be created. I apologize if I'm not asking this correctly but I have no background in fluid dynamics.

Homework Statement A person, traveling eastward at a rate of 4.0 km/hr, observes that the wind seems to blow directly from the north; on doubling his speed the wind appears to come from the northeast; determine the direction of the wind and its velocity. Homework Equations The...

This may be a ridiculous question, or we may be overlooking what is a simple answer but a friend and I can't come to a reasonable conclusion. Why does a strong wind feel colder then a gentle breeze? We have thought about the fact that this may not be the case at all and that the temperature of...

Homework Statement A pilot must travel directly to a town 500 miles away in a directions 20 degrees east of south from her present position. There is a steady 40 mph wind blowing west to east. Her plane's cruising speed through calm air is 95 mph. Using vector, what must be the plane's...

Homework Statement 30% chance of rain, 45% chance of windy, 62% chance rain OR wind. Assuming it is raining what is the probability that it is windy? Homework Equations P(wind or rain)= P(wind)+P(rain) - P(wind & rain) This does not work out the way I tried it... The...

Today this guy at work told me that a 2MW wind turbine required 20K ft lbs on the main shaft at 20 rpm. I thought that I had recently read that a 750KW wind turbine might need 20K ft lb torque. I am not looking for exact numbers but which seems correct?

I recently took a crash course that included some topics in fluid mechanics. I learned that you can use the concept of impulse and momentum the calculate the force of fluid, for instance a jet of water on a turbine blade. The equations used are: ƩFx = ρQ(Vx1-Vx2) ƩFy = ρQ(Vy1-Vy2) I...

I'm having trouble solving this problem. I'm trying to find the steady state angle of a rod with wind /fluid drag. Assume Cd, L, U, etc. are known. The viscous and form drag forces are a function of the angle θ so I don't have enough equations to solve the problem. Maybe there's some type of...

how can energy equations be applied in analyzing how is DDWFTTW- Directly Downwind Faster Than The Wind- system works? Thank you

The usual story is that after a solar flair (coronal mass ejection) towards the Earth the Earth's magnetic field gets strongly deformed. It usually takes a few days from the solar event to when the Earth is impacted. But I wonder if there is also a direct interaction: If there is drastic...

Hi, I'm sure there is a simple answer to the following question that's got me thinking lately but I'm unsure (it's more of a hypothetical question out of interest and not homework). If a simple older type fixed speed wind induction generator was connected directly to the grid via a gearbox...

Hi, I have built an 8' long wind tunnel for use in an experiment to test the effects of turbulence on several variables. However, seeing as this is an educational-level/novice wind tunnel with a fan rating of ~1800 cfm the wind speeds only really go up to ~10 mph. From my understanding, this...

I saw those giant wind turbines stopped working in winter, since winter has most wind in four seasons. so, what good comes out of that? while at least 1/4 of time in a year that the wind turbines don't generate power. and wind turbines are so expensive with limited life time around 20 years...

Hello I have designed a vertical axis wind turbine (Savonius) with a 180deg helical twist. It catches the wind really well but the wind power to electrical power conversion is really poor, it is currently only at 4% efficiency. I think the problem is the dc motor that I am using as a...

Hi i am currently doing my dissertation in which i am designing a vertical axis wind turbine design that is a modification of that of a savonius design. A major problem that i am having is being able to predict the torque value of torque for my design in order for me to then predict the...

Homework Statement An aircraft flew due east fro P to Q at u1 km/h.Wind speed from south west was v km/h.On the return journey from Q to P,due west, the aircraft's speed was u2 km/h, the wind velocity being unchanged.If the speed of the aircraft in still air was x km/h, x>v,show by resolving...

Hey everybody, I have built a 7' wind tunnel. The test section is 7''x7'' and 24" long. The diffuser opens to 22''. I would like to achieve around 30mph through the test section. I am having trouble finding a fan that can meet that need. I have looked into using an electronic radiator...

Hi forumers, I've got a question,and of course all proper answers are welcome, I think however a sailboat designer/engineer would quickly know what I'm talking about. I'd like to know what is the pressure/push of a 10 mph (16 km/h) wind on 12,000 sq.mt. surface ,and how to figure this...

How would a strain gage be set up (on top of the model? around the sting?) to measure drag? I don't quite understand the connection between the force of drag and some sort of compression/tension force...? Thanks for the clarification.

I am working on an independent study that involves housing typologies and their adaptation to climatic conditions. I am looking at row housing and how their facades may become more adaptable and responsive to changes during storm conditions. My site is beach front and prone to hurricane/ cyclone...

Suppose I've got a 6mw wind turbine with a very small wing span - 5 meters-, what would the minimum wind speed needed to activate the generator ?

Hey guys, I'm new to these forums so I am unsure if this is the right place to be posting this, but here it goes. I have been working on a drag spread sheet using OpenOffice Calc to predict where a potato will land when fired from a potato gun. I have gotten pretty far along, using...

Homework Statement Recently I've been given an assignment Build a Wind Tunnel(That can generated wind speed of 20m/s) -Izzit the chamber(whole tunnel) must be sealed ? -The material of the wind tunnel must be transparent(something like plastic?)on the test section?? Homework...

I'm in the final year of my bs. in mechanical engineering.For my senior project , I would like to conduct a study on the feasibility of harnessing wind energy for electricity in my country (I don't think it has been done here before and we have a power problem and a pollution problem). My...

Hello, I am trying to build a SIMULINK model in Matlab in order to determine the RPM of a wind turbine. Can someone please tell me how I can obtain the RPM of a wind turbine from the voltage fluctuations of a generator? Any good sites in the subject are also welcome. Thanks in advance.

this falls into civil engineering, but as we all know everything boils back to physics. and, i couldn't find any good civil forums to join. so, i have a basic Q but need help understanding some things. 1) i am building patio cover approx 50ft long x 14ft off the house. it has a pitch...

Can anyone recommend a source of information that quantifies how wind shear effects the propagation of sound/noise? I know the basics in that wind shear either bends sound waves upwards or downwards but I'm looking for something that helps calculate the effect.

This is a question that i am struggling to find any answer to on the internet. Doing some research for my 4th year honours dissertation. I have a wind turbine capable of producing a certain output at say windspeed of 10mph. Meaning that the wind is moving towards the turbine at 10mph...

Hello, My name is Ryan and I'm a volunteer instructor with the local Royal Canadian Air Cadet squadron. I'm looking for ways to try and make the kids' aviation lessons more interactive and hands on, and so I've decided I'd like to build them a small wind tunnel, purely for flow visualization...

Homework Statement Say there is a wall with width w meters and height h meters. There is a wind with velocity v m/s blowing on the wall at a 45 degree angle. The collisions of the air molecules with the wall are perfectly elastic. What is the magnitude of the force on the wall? (The density...

Nice toy... :!) A recent offshore wind turbine. 6MW peak power, the rotor has 120m or 154m diameter :-p The alternator rotates at the blades' speed, without a gearbox... With D=6.5m, it uses permanent magnets, its stator must be actively cooled, and the nacelle weighs 200t. Still not my...

Hello, For my Mechanical Engineering project, I'm working on a wind tower. One of the specifications we have to respect is a 50 years resistance to sunlight. We've chosen inox steel as the primary material (after calculating the various constraints due to the wind the the rotor up on the...

Homework Statement A boat has a sail that has a surface S towards the wind. The wind blows at constant velocity u. Also given the density of the air, p. Find the velocity of the boat as a function of time. What will be the velocity of the boat after a long enough time? What exactly is this...

Hi, Why is hight of a wind generators tower so important? Given a 50-meter tower, at what wind 'power class' and at what 'power level' will wind power be considered economical (circa 2005)?

Wind instruments exhibit overblowing: http://en.wikipedia.org/wiki/Overblowing Naively, I would expect that if one, for example, blew harder on a whistle, or blew at a different angle on a flute, the result would be as follows. You produce some noise spectrum, which becomes a different noise...

Solar wind contains ion charges and electromagnetic field, will Solar wind affect action potential within Astronaut's nerve system? Does anyone have any suggestions? Thanks in advance for any suggestions

Homework Statement Hi everyone, I'm currently in my first year of college and today I tried to calculate the wind speed of a fan by using a home made cup anemometer. In our experiment we measured the time needed for 10 revolutions, on both of the speed settings of the fan. We then converted...

Homework Statement Hi all! I am been working on an EEI. Basically I recorded the power output (P=VI) of a wind turbine with the blades at different angles. I went from 0 degrees (flat) to 180 degrees in 15 degree increments. Averaging the data I see a graph like this: Also, just to...

Homework Statement A 1.20 g spider hangs on its thread from the branch of a tree. A horizontal win blows the spider and the tread to an angle of 35 deg from the vertical. Find the force of win on the sider and the tension in the tread. Diagram...

1. Homework Statement A plane is traveling north at 200 meters/second; a wind blows from the west and accelerates the plane at 15m/s^2. If the wind lasts 10 seconds what is the plane's new velocity? 2. Homework Equations velocity = acceleration*time 3. The Attempt at a Solution v =...

Homework Statement An observer is moving to the right. A source is moving to the left. There is a wind moving to the right. What is the observed frequency? I had a quiz and this came up. I'm not sure if I did it right. Homework Equations f'=f(v±(vl-vw))/(v±(vs-vw)) The Attempt...

This is pretty simple,but finding the correct formula does not seem to be that easy for me. How could I calculate wind speeds with only having the distance an object moved over a certain amount of time and the weight of said object? For example,winds caused a 600lb object to travel 30...

I am designing a wind tunnel for my final year project. I am am now a little lost at the power requirements area. To select a fan, i understand that i have to overcome the pressure drops through out the tunnel by choosing a fan that has a higher pressure rise. So far i have figured out that i...