breaking wind silently wondering is what kind of experience? September 16, Changan Automobile with UNI-T car, in China BARI aerodynamics – acoustic wind tunnel testing room with you to explore the mysteries of wind noise. At the scene, not only 3D acoustic camera eye-opener “to catch the wind to catch sound”, but with a clay model making, testing plume interesting links in all directions to decrypt the hard core scientific and technological strength Changan UNI-T behind the design.
In the car driving, there are often such as engine noise, road noise, tire noise, and other noise, while the car during running, the shape of the body surface, and the air flow profile noise generated by the interaction occurs, i.e. called wind noise. Cars faster, the greater the wind noise. Once the speed of over 80 km / h, wind will gradually overshadowed other noise, become the most important source of noise. In the latest in a car consumer survey, consumers complained about wind noise came in TOP5, has become one of the car users are most dissatisfied with the problem. Not only wind noise bandwidth, high strength also makes it easy for passengers to feel irritable, tired, prolonged exposure to wind noise impact, but also endanger traffic safety. Research on wind noise problem
aerodynamic and thermal experts in the field of international senior management Sun network Code introduced, in order to comprehensively and systematically, must satisfy two environmental conditions. First, there is steady flow field, wind speed and wind precisely controllable source; second is the ability to exclude interference from other noise. Wind tunnel is the best choice, it is equipped with sound-absorbing material around the walls and top, and an acoustic pressure pulsation regulating process flow path, so that background noise is reduced to very low levels. In the experiment the wind speed reaches 140km / h when the ambient noise is only only 58 decibels, is one of the quietest wind tunnel.
According to him, the microphone array, also called “acoustic camera” in the left and right sides are each equipped with three microphones 168, so that the array can accurately identify a sound source out of the bus. Shooting by a camera on both sides of the upper and acoustic simultaneously, and then through the matching computer synthesized, the noise source can be distributed over the surface of the vehicle body 3D. China BARI wind tunnel laboratory is the first microphone array mounted on three sides of the wind tunnel laboratory, is one of acoustic measuring equipment of the world’s most advanced at present.
In paper clip UNI-T test day, the test person holding two paper clips, spaced only 5cm, of from about 1.5 meters in height, while loosely fall, landing moment two paper clips, the camera can see the acoustic monitoring screen two small patches appear, showing a high acoustic sensitivity of the camera; also very accurate , even if the two sound sources closely spaced, it can also be clearly identified. Protect the car noise source identification test of precision and reliability.
“wind noise test apparatus includes an artificial head, and the spherical surface of the microphone array.” International experts aerodynamic and thermal management field Sun network Code introduced human artificial head mainly collected car when the real feel of noise in the test, will be placed in the front driver and passenger seat. Artificial head binaural acoustic sensors mounted position, so that when recording sound may simulate the effects of shoulder, head and ear and other parts of the sound field, the human ear is closer to the playback actually heard sound signal; ball grid array in the test will be placed inside the cockpit to help isolate the vehicle and a noise sound source distribution leakage position; microphone attached to the surface of the body surface, the pressure pulsations acting on the measuring body surface. Three devices are designed to assist the most comprehensive data in wind noise experiments to identify problems and make improvements.
The most important part of the field test later than the acoustic camera, open test, you first need to adjust the speed of the wind speeds required for testing, do a test wind noise when the wind speed will usually set at 80-140km / h hour wind speed setting usually live acquisition 120km / h, and artificial acoustic camera head data of about 30 seconds, the computer will complete the acquisition of raw data for further processing, and to obtain the required information. Testing can be seen at different wind speeds, the different frequency UNI-T wind noise test the noise is not the same, the size of the noise source may be determined, and gives the ear feel different frequency spectrum by the noise screen are different . On the whole, Changan UNI-T at 120 km / h of wind speed, wind noise is still achieved good test scores, in a relatively good level in the industry.
“breaking wind silent,” Chang UNI-T team is how to do?
was able to achieve excellent wind noise test scores, Changan UNI-T totalMonitoring Yong Qin respectively around the mirror optimization, and optimization tail plume testing aspects of the Secret.
Yong Qin, UNI-T at the beginning of the design, modeling programs have to analyze the different aerodynamic quality by CAE simulation to find improved design problems, and, to the actual test and the clay model by further modeling adjustments. For example in order to optimize the rearview mirror, rearview mirrors were only wind noise optimization, modeling it involves multiple departments, regulations, CAE and product, whether good-looking style, vision meets the regulatory requirements, the final adjustment is able to complete wind noise compliance requires collaboration and cooperation with various departments, a tiny change required the joint efforts of countless people behind. By optimizing the rearview mirror, the overall sound pressure level at the driver’s ear will be reduced 0.3dB (A), enough to appear Chang CFD technical strength. Such details of the optimization on the myriad of UNI-T, all of this 0.3dB (A), add up, eventually produce a qualitative change.
As one of the logo design of UNI-T, UNI-T tail design is very special. Such advanced design, also pose a particular challenge to the team. After all, from an aerodynamic point of view, tend to make all the cars are designed to shape a way, but this is clearly not what consumers want to see, therefore, aerodynamics’s mission is to make each form different design, are able to have a good aerodynamic performance.
Since the tail using a hollow design, the air flow will impact the roof through the holes and the V-shaped channel downwardly to the rear window, formed of a large wind noise. The first time I saw this design, the team held an emergency meeting, has repeatedly demonstrated the feasibility and risks, and calls the 4000 nuclear simulation resources, calculating the amount of more than 1 million CPU hours. If the change in the market of high-performance personal computer processors, computing need to keep more than 12 years, and the core HPC server 4000, the entire compression calculation cycle to 20 days. Before and after doing the calculation over 60 optimization, and ultimately find more than 20 active programs, dramatically reducing the wind noise generated by the tail.
Tan Yong said smoke flow tests are flow visualization tests the most common testing means, to restore the earlier V-tail with the clay in the clay model engineer the design, can be seen in different shapes by smoke flow test empennage affect the flow field. In the early design of the tail due to the negative pressure generated rear, The tail part of the air from the hollow drill down portion, a turbulent flow, a greater pressure pulsation, and transmitted through the windshield to the vehicle, bring more wind noise; final goods vehicle tail state of the other side, although the same is hollow design , but the airflow through the rear portion of the roof, the duck tail gas stream rise, the rear fin better to form a ramp to guide air flow, the air flow downward trend slap rear window have been alleviated, the wind noise is effectively reduced.
upstream news – Chongqing Morning News reporter Liu Hanshu