Visualization Techniques in a Wind Tunnel

Visualization Techniques in a Wind Tunnel

wind tunnel visualizationThe needs of aircraft designers and aerodynamicists have begun to grow at a pace that requires changes in equipment and techniques used by those that produce aerodynamic data for the design of aircraft. New techniques of flow visualization have been developed, and as technology improves, new techniques will become more widely available in tunnels throughout the world.

Older flow visualization techniques are still, in large part, standards being used in almost every model test. These visualizations include:

Smoke:

This is a classic visualization that most are already familiar with.  This technique involves sending a stream of smoke down the wind tunnel, allowing researchers to see how airflow interacts with a model in real time. This method can be used with any type of model and in almost any type of wind tunnel.

Tufts:

This technique involves the use of a filament or string attached in either a few or many positions on the model. Tufts are similar to blades of grass moving in the wind, and many types of tuft installations will use a dye or luminescent coating that allows movement to be tracked in regular light.

Oil:

wind tunnel oil flowOil is generally dyed and applied to the model prior to turning the wind on in the tunnel. This technique leaves a removable pattern of surface flow on the model after the test mode is completed. This solution also precludes the model from changing position during wind-on time, to ensure that the oil residue has stabilized over the area of interest. This technique has been used since the inception of wind tunnel testing, and clearly illustrates how wind flow interacts with an aircraft. Oil pools up or forms streams during low friction, such as flow separation on a wing, and areas that experience high friction (like that of a vortex) will be clear of oil.

Schlieren:

Schlieren flow visualization is based on the principle that light rays bend when they encounter changes in density. This technique stands to benefit from future technologies; however, historically, these images are 2D in nature, while the shockwaves that they are recording are 3D. This creates an interpretation problem for many engineers, and maybe one of the more difficult visualization methods to both understand and utilize.

Many older techniques are being improved with technology and better data collection processes to improve the output of wind tunnel tests. Although not every technique on this list is new, advances in capture and application technologies have improved their output to a degree not possible before.

Techniques on the cutting edge:

Pressure sensitive paint (PSP):

This flow visualization technique is a process of applying paint that is pressure and temperature sensitive, often by using O2 interaction with luminescent molecules within the paint itself. This technique allows researchers to understand highly complex flow patterns in relation to pressure and temperature. This also means that researchers can study more than just flow effects over a surface.

Laser Sheet:

Laser sheet visualization is accomplished by saturating the wind tunnel upstream with a particulate that will be illuminated by light. Lasers are generally used as a light source because the light quality is both uniform and measurable. Laser sheet visualization is primarily used to track airflow after it has made contact with the model, this helps understand vortices and the effect of air throughout a model’s motion.

Digital Particle Image Velocimetry (DPIV):

This technique is one of the largest beneficiaries of faster computers and the readily available processing power needed to analyze a complex series of images. The airflow surrounding the model is unaffected by DPIV and laser sheet imaging, which means that this process is becoming one of the more attractive options for gathering visual data. DPIV uses pulsed laser sheets to scatter light off of particulates (oil droplets, smoke particles, etc.) that are seeding into the flow field. The scatted light is captured by digital cameras to determine each particles positions with the two dimensional light sheet. By pulsing the laser and camera twice in rapid succession, it is possible to determine the movement of the particles between the two images. Using powerful computers, the correlation between the particles in the successive images is determined for the entire flow field and a two dimensional map of the flow field velocity is created. Utilizing the flow velocity data from multiple image pair, investigators, can create an understandable database of information used to validate a model or illustrate changes that must be made to the design.

 

Many techniques are available to visualize data within a wind tunnel, and as technology improves, these methods will become faster, more readily available, and more dependable. Visualization is only a small part of the wind tunnel data gathering process, but it is an important component of any aircraft or spacecraft design.

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Adding another aircraft to an ever-growing fleet allows Calspan to better address the needs of an evolving customer base.

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Multi-point data collection creates incredible detail

Buffalo, New York – October 31, 2017 – Calspan is pleased to announce the acquisition, modification, and certification of a long-range fixed-wing unmanned aircraft for the purposes of aerial surveying, LIDAR mapping, and 3D photography. This new unmanned aircraft allows Calspan to enter emerging markets that service public utilities and government agencies.

Unique features of Calspan’s unmanned system consist of a 20+ hour flight duration, modular payload system, and fail-safe parachute recovery system. These features make the drone a safe, cost effective and flexible solution for customers seeking accurate, real-time data collection capability.

Calspan has also acquired the relevant licenses and approvals from the Federal Aviation Administration for commercial drone operations under CFR Title 14 Part 107. This step is required for safe operation of the drone within the national airspace system.

Lou Knotts, CEO of Calspan, stated “As a global leader in aviation innovation for more than 70 years, Calspan is excited about developing small unmanned aircraft technology to meet the needs of the markets we serve.”

The drone operation will be based at Calspan’s 80,000 sq.ft. Aerospace facility at Niagara Falls International Airport, in Niagara Falls, New York. The drone will be transported to various locations in western New York and Pennsylvania for missions aimed at monitoring the status of pipelines, rights-of-way, waste storage facilities and other infrastructure components that belong to government agencies and public utility companies.

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Calspan’s unmanned aircraft is capable of extended flight time and higher payload capacity

As a part of this project, Calspan is developing sensor payloads, beyond-line-of-sight communications systems, and other related equipment that can utilize the drone’s long range capability. In addition to conventional imaging, the sensor suite will include infrared photography, real-time video, LIDAR, and gas leak detection.

Follow these links to learn more about Calspan’s unmanned aircraft services:

Unmanned services overview

Right of way management

 

About Calspan
For more than 70 years, Calspan has been providing research and testing services in the aviation and transportation industries and is internationally recognized for research and innovation. Calspan is privately owned with its headquarters located in Buffalo, New York where they maintain a variety of testing facilities including a transonic wind tunnel, a vehicle crash test operation, a HYGE sled used for child seat testing, and a high performance tire testing facility. Calspan also operates a flight research and testing facility at the Niagara Falls International Airport where they own and operate a number of aircraft used as in-flight simulators and airborne testbeds.

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Milcom

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Calspan is excited to be attending MILCOM 2017 as an exhibitor.

MILCOM is a conference for global military communications professionals, giving industry leaders the opportunity to hear and understand the requirements, pace of change and state of play in a variety of C4ISR markets serving the military, federal agencies and multinational entities.

The MILCOM 2017 theme is Military Communications and Innovation: Priorities for the Modern Warfighter. Conference attendees will have the opportunity to attend over 200 unclassified and restricted sessions lead by experts in C4I and cyber issues as well as specialists in science and technology developments.

For three days, Calspan will join over 100 other exhibitors who provide technological support for aviation, military communications, intelligence and surveillance at the Baltimore Convention Center.

We plan to connect with individuals who might be interested in our in airborne research, development, test & evaluation (RDT&E) abilities. Which includes in-flight simulation, unmanned air vehicle (UAV) surrogacy, and the ability to attach external stores of up to 2,500 lbs on our Gulfstream III airborne testbeds.

Calspan’s Gulfstream G-III is specifically designed to support large-scale testing of avionics, radar and sensor systems, handle large Fire Control Radars, Electro-Optical/Infra-Red (EO/IR) sensors and other heavy external stores. At MILCOM, we’ll be demonstrating roll-on, roll-off capabilities and have examples of what our Gulfstream G-III is capable of.

Calspan also has a fleet of Learjets that are used for in-flight simulation. Each aircraft is equipped with a programmable Fly-by-Wire Flight Control System (i.e., Variable Stability System) that allows for modification of the dynamics of the base Learjet airframe. While the aircraft have been used for manned aircraft handling qualities evaluations for decades, the programmable nature of the VSS allows the aircraft to be used as UAV surrogates to test the latest in unmanned aircraft technologies.

If you or someone you know is attending MILCOM 2017, October 23-25 at the Baltimore Convention Center, stop by and say hello to Calspan. We’ll be at Booth 817 – near the exhibition hall entrance, across from MilDef Inc.

To learn more about our in-flight simulation abilities, visit Calspan.com.

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Film Pit

Calspan and MESSRING partner to provide automotive test solutions

Coming together to fulfill the growing North American demand for crash test services and equipment

Buffalo, New York – On September 26, 2017, Calspan and MESSRING announce that a partnership agreement has been established between both companies. This partnership fulfills a growing market need for automotive crash test services and the associated specialized equipment in response to the recent increase in the number of vehicular fatalities year over year. Against the backdrop of the largest yearly increase in deaths from car crashes since 1975, and with the U.S. Department of Transportation considering a major upgrade of the U.S. New Car Assessment Program (NCAP), automotive manufacturers and suppliers must begin to invest in crash test facilities, services, and equipment to develop safer vehicles.

The complexities involved with building a new or upgrading an existing crash test facility are widely variable. The types of testing, types of vehicles that can be tested, and the ability of the facility to conform to future requirements all factor into proper crash facility design. A partnership between MESSRING and Calspan will provide customers with a singular point of contact, resulting in a best value solution. Together, they will jointly present customers holistic solutions which encompass identifying and acquisition of suitable real estate, conceptual crash lab design, specialized crash lab equipment, and construction management.

Furthermore, to minimize the impact that downtime can have on a lab being upgraded, Calspan will provide crash test services and test specific training on MESSRING equipment, making the transition for the customer seamless. Under this agreement, Calspan will also perform calibrations on MESSRING load cells, DAS products and speed traps.

“Calspan is well known for its exceptional engineering, crash test and calibration services; including the successful execution of complex NHTSA frontal oblique crash tests using T.H.O.R crash test dummies. This partnership in combination with Calspan’s new, state-of-the-art and highly secure crash facility, which is outfitted with MESSRING’s equipment, positions Calspan to meet the needs of regulators, traditional OEM’s, safety restraint suppliers and EV / start-ups” stated Jerry Goupil, Director of Crash Testing, Calspan.

“MESSRING is proud to continue a long history of providing the highest performance crash test equipment in the world. A partnership with Calspan extends our serviceable reach throughout all of North America. We will be able to provide our customers with a higher level of service, and a closer point of contact with the services that support our equipment” stated Mr. Corey Miller, Vice President, MESSRING North America.

About Calspan

For more than 70 years, Calspan has been providing research and testing services in the aviation and transportation industries and is internationally recognized for research and innovation. Calspan is privately owned with its headquarters located in Buffalo, New York where they maintain a variety of testing facilities including a transonic wind tunnel, a vehicle crash test operation, a HYGE sled used for child seat testing, and a high performance tire testing facility. Calspan also operates a flight research and testing facility at the Niagara Falls International Airport where they own and operate a number of aircraft used as in-flight simulators and airborne testbeds. For more information about Calspan, please visit https://www.calspan.com.

About MESSRING

MESSRING in Krailling, close to Munich is the world’s leading manufacturer of crash test systems and components. The mid-size company designs and builds turnkey test systems for customers in all relevant markets and on nearly all continents. To date, MESSRING has implemented more than 100 large crash test systems for automotive OEMs, automotive suppliers, governmental authorities and insurance companies – more than any other company. In the process, the global market leader continues to astonish the industry time and again with innovative advances and revolutionary new solutions, whether in system design, the actual measurement equipment, or in documentation and recording of individual tests. For more information, go to www.messring.de

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10/26/2017

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Aerospace / Blog / Wind Tunnel

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