The drag on a 2-m-diameter satellite dish due to an 81-km/hr wind is to be determined through a wind tunnel test using a geometrically similar 0.4-m-diameter model dish. Assume standard air for both model and prototype. (a) At what air speed should the model test be run

The correct answer is - 405 km/hr

Explanation:

given:

2-m- = diameter satellite dish

81-km/hr = Y

0.4-m- = diameter model dish.

Reynolds number is essential for this, thus,

Vm Dm/vm = VD/v

(D is the diameter of the dish)

Vm = (vm/v) (D/Dm) Y

and if vm/v = 1, then

Vm = (2/0.4) (81)

= 405 km/hr

Thus, the correct answer is - 405 km/hr

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia

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