I have a bunch of this stuff and want to use it for support under some sagging pipe what orientation would it be more supportive to span 10' ?

Thanks!

That is perforated Unistrut (shallow strut), have used miles of it installing conduit, tubing, and piping. Get yourself some Unistrut straps (whatever size you need), and use it just like the image (pipe on top). The bottom of the straps slide into the groove in the strut and clamp over the pipe.

Not really enough info to give you an engineered answer but it can hold up a fair amount of weight. The questIon I think your asking is related to deflection, which is more a question of what intervals do you need to install the unistrut at. What length of pipe, material, sch, etc?

Sideways. However there is two depths. You have pictured the shallow version. If it is the shallow version, you may need center support. Even sideways. You could even build a T type rail. There are a number of unistrut builiding brackets.
You can use selfthreading Tek screws to build with. You may need to predrill a small pilot hole.

Channel up or channel down, 10 ft is big ask for shallow.

How are you going to support the strut, what kind of brackets (hanging all thread for trapeze brackets, angle iron T or L brackets, screwed/bolted directly etc etc)? Shallow Strut isn't nearly as strong as standard (solid) Unistrut, but if supported properly it can hold quite a bit of weight. How much/what kind & size of pipe are we talking about? How long are your pieces of strut going to be?

Depends on pipe. Metal or plastic (PVC)?

Found a bunch of the bigger Unistrut that I didn't know we had so we'll use that. Going to support 4" PVC the couplings sit on stacked cinder blocks 10 feet apart.

Thank you for your help

Good deal amigo.