Consider water flowing in a pipe, and I don't know the direction of flow. How to determine the direction of flow? My approach- I can use a pitot tube but for that I have to drill a hole in the pipe and I can't use this approach for fluids whose leakage will create a severe problem.
What is the simplest way to determine the direction of flow?
Edit- Is it possible to determine the flow direction without using gauges or any specific instrument?
Heat the pipe at some point, and find the direction in which heat transfers. This will give you the direction of the flow.
Caution: Don't do this for flammable fluids. Thanks to @Carl Witthoft for pointing this out.
Yes, purchase an ultrasonic flow meter.
Needs a straight length of pipe and very careful placing of the sensors. However, if done well one can get good results, if not then the results can be spectacularly poor.
If this is a pumped system, try measuring the reaction forces when you turn the system on. For example, if you're trying to measure the direction of fluid flow in a hermetically sealed "black box" type device, put the device on a turntable and turn the device on. Depending on the direction of rotation of the turntable, you will know if the fluid is flowing clockwise or counterclockwise.
Look at or develop a flow schematic of the system. A cursury examination should give most likely flow direction. Maybe some existing ancillary measurements could give you necessary info.
