The Hessert laboratory space is divided between a Main Lab on the upper level, and smaller labs on the lower level. The concept of the Main Lab is an outgrowth of the old Aerospace Laboratory in which the facilities and associated instrumentation are shared among the users. It consists of a large common space that houses the facilities. A photograph of the Main Lab is shown to the left.
The Main Lab houses three open-return wind tunnels, an Environmental Wind tunnel, three tri-sonic wind tunnels, a 1m cross-section test section closed-return wind tunnel, an anechoic open jet wind tunnel, and a high-pressure blow-down facility. All are shared by members of FlowPAC.
The three open-return wind tunnels have test sections that are 0.6m by 0.6m by 2.7m long. The test sections are modular and removable so that experiments can be set up off-line and then rolled into place when ready. The free-stream speed range of these wind tunnels is 2-40 m/s. An example of these open-return wind tunnels is shown on the left.
Hessert Laboratory is also home to three tri-sonic wind tunnels. These wind tunnels are connected to a pair of large vacuum pumps. The RPM of the pumps is individually controllable so that the air pressure at their inlet can be adjusted from slightly below atmospheric to a maximum vacuum of 0.5 atm. The general operation for these wind tunnels is to draw air from the lab space at atmospheric pressure. The design Mach number in test sections is then based on the inlet nozzle design and cross-section area. Test sections exist for a range of Mach numbers from 0.1 to 1.4. At Mach 1.4, the test section cross-section is 10 cm by 12 cm, and the operation time is unlimited. The tri-sonic wind tunnels are supported by a color Schlieren optical system.
The Environmental Wind Tunnel is a semi-closed-return design with a large long test section. The photograph on the right shows the wind tunnel test section. The test section dimensions are 1.2m by 1.5m by 10.6m long. The maximum air speed in the test section is 20 m/s. The long test section was primarily designed to provide a long roughness fetch to develop thick turbulent boundary layers that can simulate a neutral atmospheric boundary layer. Models of buildings can be placed on a rotating turn table at the downstream end of the test section to simulate different wind orientations. The wind tunnel can also be used to study the transport of scalar contaminants.
The long test section is useful for aerodynamic experiments that require long development lengths. An example is the interaction between two wing-tip vortices that are shown through flow visualization in the following right photograph.
The anechoic open jet wind tunnel is a draw-down design with the test section placed inside a large anechoic chamber. The air enters the anechoic chamber through a series of turbulence management screens and a large area-ratio contraction. A fan at the opposite end of the anechoic chamber draws air through the wind tunnel. The maximum test area velocity is 35 m/s.
The anechoic room is 9.14m (30 ft) long by 7.32m (24 ft) wide by 3.66m (12 t) high. The anechoic treatment consists of 55.88 cm (22 in) thick acoustical-fiberglass wedges on all six sides of the room. The room was designed to have a low-frequency cutoff of at least 150 Hz. Above the cutoff frequency, the wedges have a coeffcient of energy absorption at normal incidence of 0.99 or greater.
Wind tunnel models are placed in the open-jet flow stream, and arrays of microphones are used to measure the aerodynamically generated sound. Optional side wall can be placed around the open jet as necessary. The instrumentation for this facility includes two multi-microphone phased arrays, and other acoustic and flow measurement systems.
The High-pressure Blow-down Facility consists of a 550 psi two-stage compressor that provides compressed air to a 7.5 cubic-meter storage tank. Prior to storage, the air passes through a desiccant dryer to remove moisture. The air from the storage tank is delivered to an exhaust manifold through 15.2 cm I.D. steel welded pipe. Pressure-regulated valves in the piping system are used to maintain a specied exit flow rate. The facility can operate continuously within the flow rate capabilities of the compressor. Alternatively, it can be operated in a transient mode where the storage tank is pressurized and air is released at a flow rate that is set by the pressure-regulated valves. The run durations in these cases depends on the flow rate.
An example of an application for the High-pressure Blow-down Facility is in the control of transonic jet noise. The transonic jet noise setup is shown in the following photograph. The photograph on the left. an array of hot-wire sensors that was used in constructing the coherent turbulent structures in the jet flow. The room where the facility is located allows a portable anechoic environment to be placed around the experimental setup.
A new closed-return wind tunnel with a 1m by 1m by 3m long test section and a maximum velocity of 80 m/s is presently under construction in the Main Lab. The dimensions and design of the test section are identical to the test section of the Mach 0.6 wind tunnel in our White Field Laboratory. This will allow an easy exchange of the models between the two facilities.
The lower level of the Hessert Laboratory includes smaller individual labs that are aimed at more focused research. This includes a laboratory for charged particle and multi-phase flow research, turbo-machine research, aero-optics research, and flow control actuators and sensors research. Examples from these laboratories are shown in the following.