[aerohead]

A water table would allow qualitative flow investigations in 2D flow.
For 3D flow you need a water tunnel, since our cars are 'completely-submerged' bodies on the tropospheric ocean floor.
Long ago, Myth-Busters created a sort of water tunnel from a shallow pool with an inside partition, and used a battery-powered trawling motor to circulate the water, in a continuous stream.
Very small Tygon tubing can be arranged within the model, to inject food coloring into the stream for flow imaging. We used this at Texas Tech for both the water table, water tunnel, and underwater tow-tank.
When the water gets murky, a shot of bleach instantly clears it up.
With SCUBA goggles you could observe your model while you inject the 'dye' with a squeeze-bulb.
You'll never be able to 'measure' forces, but you will be able to observe flow at a proper Reynolds number, with just a couple of mile per hour flow velocity.