Facilities

Re-Circulating Water Tunnels

NAHL now has two water tunnel/channel systems: 

Large Re-Circulating Water Tunnel:

The Large Re-Circulating Water Tunnel has a free-surface and is used mainly for cavitation and flow visualization studies.  It is also used for the measurement of forces and pressure distribution on hydrofoils, rudders, and submerged bodies. The test section pressure can be varied from +5 to -10 PSI (+35 to -70 kPa), which allows for the demonstration of cavitation effects on propellers and hydrofoil sections at lower speeds.

TEST SECTION: 1.3 FT X 1.3 FT X 5.0 FT (0.41 m X 0.41 m X 1.50 m)

DESCRIPTION OF FACILITY:

Vertical, closed loop with free-surface test section.

TYPE OF DRIVE SYSTEM AND TOTAL MOTOR POWER:

4-bladed axial flow impeller; 75 HP (56 kW), 1750 RPM.

INSTRUMENTATION:

Water velocity via pitot tube or contraction; static and dynamic pressures; propeller RPM; forces.

TESTS PERFORMED:

Cavitation and flow visualization; force; moment and pressure distribution on hydrofoils, rudders, and submerged bodies.

Small Re-Circulating Water Tunnel:

The Small Re-Circulating Water Tunnel has two interchangeable test sections.  One was optimized for low turbulence, which allows for detailed studies of flow within the boundary layer.  The other was optimized for evaluating the friction of test surfaces using static pressure measurements along the length of the test section.

DESCRIPTION OF FACILITY:

Vertical, closed loop, closed surface.

TYPE OF DRIVE SYSTEM AND TOTAL MOTOR POWER:

Two centrifugal impeller pumps, 5 HP each, 1750 RPM; 10 HP Total (7.5 kW).

INSTRUMENTATION:

Particle Image Velocimeter (PIV), Laser Doppler Velocimeter (LDV), pressure measurement.

TESTS PERFORMED:

Flow studies of boundary layer and around submerged objects; surface friction measurements.