Defense

February 14, 2014

Tunnel 9 engineers conduct boundary layer transition experiments at Mach 10

Air Force Project Engineer and Purdue University graduate student George Moraru examines the illuminated temperature sensitive paint coating on the large, 7-degree cone prior to the test program. The testing is performed under the Test Resource Management Center and the Air Force Office of Scientific Research funded Hypersonic Center of Testing Excellence.

The Arnold Engineering Development Complex Hypervelocity Wind Tunnel 9 is performing experiments on a large 7-degree cone test article at Mach 10 to improve the understanding of hypersonic boundary layer transition in testing and evaluation facilities.

The testing is made possible under the Test Resource Management Center and the Air Force Office of Scientific Research funded Hypersonic Center of Testing Excellence.

According to Dan Marren, White Oak site director, this program was modeled after the AFOSR lab programs and is the first of its kind for the test and evaluation commands.

“The first CoTE pilot program is in the area of hypersonics and is located at AEDC White Oak because of the unique hypervelocity test facility (Tunnel 9) located there. The University of Maryland was chosen as the anchor university,” he said. “The basic vision of this program is to bring together researchers, students and testing professionals working on U.S. Air Force priorities in a collaborative way that strengthens the vitality of both the research and the work force.”

The experimental program conducted during the Fall-Winter 2013-2014 consists of approximately 20 Mach 10 runs at units Reynolds number between two and 10 million per foot. High fidelity measurements are required to make better flight predictions based wind tunnel measurements and to validate boundary layer stability computations. Such computations offering predictive capabilities and their validation based on wind tunnel data are essential to reduce the developmental risks of new hypersonic systems. The ability to predict whether or not a vehicle will maintain a laminar boundary layer while travelling at hypersonic speed is critical. For turbulent boundary layers, the heating rate and viscous drag both increase sharply leading to more stringent thermal protection requirements, a reduced range and/or increased propulsion requirements.

Previous measurements in large scale hypersonic T&E facilities over the last 40 years were mostly limited to the determination of the transition location and provided limited insight into the physics of the transition process. Several cutting edge measurements techniques providing new insight are used during this test campaign including temperature sensitive paint, high frequency response pressure sensors and high speed Schlieren cinematography.

A new high speed data acquisition system is being deployed during this program to simultaneously acquire signals from 90 pressure transducers at sample rates between two and 10 MHz. Pressure measurements at frequencies up to 1 MHz are required to measure the acoustic instabilities (2nd mode wave) propagating and growing inside the laminar boundary layer and their breakdown which leads to turbulent flow. Such measurement can be achieved using high frequency response piezoelectric pressure transducers. The high density of pressure transducers on the cone test article allows the determination of the spatial amplification rates of instabilities which can be directly compared against boundary layer stability computations. In addition to point measurements, TSP provides global surface heat transfer to reveal detailed information about the shape of the transition front and transitional flow features such as crossflow vortices.

The 61-inch long cone model is fitted with interchangeable nose tips with radii between 0.06 and two inches in order to assess the effect of nose bluntness on boundary layer transition. Previous measurements have revealed that transition moves downstream with an increase in nose diameter. Such measurements have been corroborated with stability computations showing reduced second mode growth with increased bluntness. However, high fidelity instability measurements have yet to be performed for a wide range of nose bluntness.

The effect of small angle of attacks on the shape of the transition front is not well understood. This effect is investigated by using the unique Tunnel 9 hydraulic pitch system which allows measurement over a wide angle of attack range during a single wind tunnel run. Measurements at angles of attack up to 10 degrees are performed to quantify the effect of crossflow instability on the transition process.




All of this week's top headlines to your email every Friday.


 
 

 

Hurricane Hunters to fly Tropical Storm Erika

The Air Force Reserve Hurricane Hunters are operating out of Homestead Air Reserve Base, Fla., flying their state-of-the-art WC-130J Super Hercules into Tropical Storm Erika in support of the National Hurricane Center in Miami. The 53rd Weather Reconnaissance Squadron flew four missions into the tropical storm from their deployed location at St. Croix in the...
 
 

Pentagon probing alleged distorting of war intelligence

The Pentagon’s inspector general is investigating an allegation that the military command overseeing the anti-Islamic State campaign distorted or altered intelligence assessments to exaggerate progress against the militant group, a defense official said Aug. 26. The official was not authorized to discuss the probe publicly and so spoke on condition of anonymity. The investigation was...
 
 
LM-C130

U.S. Air Force receives additional MC-130J Commando II

MARIETTA, Ga., Aug. 27, 2015 – A crew from the U.S. Air Force Aug. 27 ferried a new MC-130J Commando II aircraft assigned to Air Force Special Operations Command to Cannon Air Force Base, N.., from the Lockheed Martin facilit...
 

 
af-uav4

Arming the RPAs

Air Force photograph by TSgt. Joseph Swafford A1C Matthew Lopez (center), 62nd Expeditionary Reconnaissance Squadron munitions systems technician, builds a GPS-guided GBU-49 bomb at Kandahar Airfield, Afghanistan, Aug. 15, 2015...
 
 
dragon-lady1

Local efforts help keep Dragon Lady flying at 60

Air Force photograph by Airman 1st Class Bobby Cummings A U-2 Dragon Lady soars above the flightline at Beale Air Force Base, Calif., Jan. 22, 2014. The low-altitude handling characteristics of the aircraft and bicycle-type lan...
 
 
Air Force photograph

U.S. Navy awards production contract for additional P-8A aircraft, first RAAF planes

Air Force photograph A P-8A Poseidon maritime patrol and reconnaissance aircraft parked on the tarmac during a BALTOPS 2015 mission on the flightline of Spangdahlem Air Base, Germany, June 9, 2015. The U.S. Navy awarded a nearl...
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>