Probe/Anemometer for Measuring Flow Speed and Direction?

Can you use a tracer gas and high resolution video?

Thank you for your reply!!

I will be using smoke for flow visualisation later. However, it is difficult in getting a numerical value for the velocity field using this method, especially if I want to measure the velocity of a slice of the mid plane. I will be using PIV in the water channel, however, the reynolds number achieved in the water channel will be significantly lower.

A cheap weather station will do that.

They even can be wireless and download data to your PC.

Thanks for the suggestion.

My fault for not clarifying. I need something that has high spatial resolution. My bluff body, which is a 1/15th scaled model of a freight train wagon is about 1000mm X 171mm X 438mm (LWH). So I really need something really small such as a cobra probe or hot wire anemometer in order to measure flow velocity at various spatial points at fine increments behind the model.

Cobra probe was great for the most part until it comes to recirculating flows.

You're right that hot wire type doesn't tell you direction, if that's any help.

At what velocities is your rig supposed to run? At higher velocities you design to run your rig, you may use IR imaging. Velocities have relationship to pressure and pressure of a medium fluid relates to temperature.

A temperature signature could be used to analyze your velocities, any point of your bluff body you like to focus your concerns to.

My wind tunnel is running at 30m/s. What speed will I need for IR imaging? Cheers

Ahhmmmsubsonic~supersonic, probably.

Try a pitot tube, static tube combination, you can position it anyway you want as long as the static tube opening is at right angles to the flow. A hot wire anemometer has to be re-calibrated for its enclosure if it's in anything other than free space

Don't know about "A hot wire anemometer has to be re-calibrated for its enclosure if it's in anything other than free space". What sort of recalibration?

A big advantage of a thermal type flowmeter (velocity x pipe area) is it doesn't need correction for gas temperature and pressure, unlike say a ΔP type meter. It's often called a thermal mass flowmeter.

I don't know if you can get one small enough, but ultrasonic anemometers can measure speed and direction.

http://www.ammonit.com/en/products/sensors/ultrasonic-anemometers

Hey guys, thanks a lot for all the inputs so far!! really appreciate it.

Some one suggested me looking into Omniprobe: http://www.aeroprobe.com/probes/view/omniprobes

It has an acceptance range of up to 150degree. I am starting to look into that, the question now is if it comes in a small enough size.

Is anyone here familiar with Omniprobe's operation?

That looks like a great solution. According to the pdf, the tips are available down to 1.6mm diameter so that would definitely be small enough for what you want to do.

You need to be able to measure 12 pressures simultaneously or in quick succession. Or maybe you buy the complete thing that does all of that. I can see it being quite expensive though. Is the Uni willing to spend some money on this?

I think the Omniprobe comes with its data acquisition system. We have pressure measuring transducers ourselves which has 128 channels, so we can also use that to hook up the 12 pressure taps.

But yea, expensive is definitely the first thing that came to mind. We to have commercial funding on this project, so we will look into it. But we might attempt to make something similar in our workshop and calibrate it ourselves.

http://www.meacon.co.za/Weather%20Instrumentation/weather/principleofoperation.htm

Interesting!

Try these guys:

www.kulite.com/products.asp?p=4-0

We used a LOT of their products in wind tunnels when I was in the aerospace business.

You may want to look at a Shortridge ADM870

Do you know anyone with CFD software?

You could input the measured vales and let the CFD calculate the rest.

Have you tried a 5 or 7 hole probe?