The first high-efficiency algorithm for the transonic flow aerodynamic noise of the rotor of the Northwestern Polytechnic University, Song Wenping, Han Zhonghua. Yang Aiming, Qiao Zhide, Center for Airfoil Research, Northwestern Polytechnical University, Xi'an 710072, China Based on the equation of 1 pillow for unsteady rotor hovering, using the 吖 formula to calculate the far field of helicopter hovering flow, production. In this paper, the method of selecting the delay time of the sound source point of 1., 0 surface is studied, and the middle is proposed. , 1 mountain 1.

The equation is solved. He 0, and the physical parameters and its space method wizard, the efficient dimensional linear interpolation method. For the helicopter rotor, the far-field noise of the flow is calculated by quantitative calculation. The calculated results are in good agreement with the experimental values. The correctness of the method is verified. In the helicopter rotor design, reducing noise has become increasingly important. The design goal, and how to accurately determine the aerodynamic noise caused by the rotor and analyze the factors affecting the noise, is to carry out the quantitative calculation of the aerodynamic noise of the wing hovering flow of the rotary goods noise reduction design, taking the mouth 1 post fixed wing as an example, calculate The transonic far-field noise is compared with the experimental results, which is in good agreement. The method is simple and accurate. It has a good 1-way application prospect for noise calculation. The main idea of ​​the method is the taxi field. Decomposed into near-field and far-field in the near-field nonlinear 1 source region 1 using the 0 method to directly solve the unsteady equation to obtain near-field noise, while in the far-field linear region, 拴, 曦, ,, 蠼庹庋 窍咝 窍咝 跋 跋 跋 跋 跋 跋 跋 跋 跋 跋 跋 跋 跋 跋 跋 跋 跋 跋 跋In the same way, the diffraction and aggregation effects of sound waves are considered. 1.1 The unsteady constant 16 equation solution The flow in the helicopter hovering state can be regarded as the quasi-steady flow, that is, the pressure distribution of the blade in the fixed coordinate system of the blade Field information is independent of azimuth.

Use algebraic methods. The generalized infinitely trapped paradox. The type 1 and 1 of the blade are wound along the radial direction of the blade, and the grid surface is approximately cylindrical. The curved surface is fixed by the blade. The governing equations of the Euler equations in the coordinate system are transformed into the rotating coordinate system with the projection of the absolute physical quantity in the relative coordinate system as parameters. The finite volume space discretization and the step-by-step beer propulsion format are directly solved, and the local time is used. Techniques such as step size and implicit residual smoothing accelerate convergence 23!

The Yangshuo Paddle Public Stop Flow Calculation Grid 1.2 uses the illusion, and the formula calculates the far-field sound pressure illusion is a integral type, which is used to calculate the sound pressure signal of the far-field observation point. The concept of sound pressure is 6, the date of receipt of 2000 0829 fund project aviation science fund 98 people 53002 and the national key laboratory fund 98 圯 51.3.1.; 5103.iI between the North 1 industry; the journal is strong. The following Wenyuzhou; Dailing friends choose a control integral surface 5, that is, 1. The surface contains the rotor blade, that is, the noise source of all nonlinear flow effects. This integral surface divides the sound pressure into the sound. In the outer two domains, the near-field sound field in the 枳 plane is directly derived from the unsteady 161. equation, the parameters used on the integral plane are obtained by solving the unsteady Euler equation, and the sound wave is considered to be linearly propagated externally. That is, from the integral face to the far-field speed of sound, it is a constant. At a certain moment, the sound at 1 at the observation point can be determined by the formula as the direction of the Mach direction at the integral plane as the direction of the velocity, which is the normal unit vector of the integral plane, and 〃 is the radius of radiation from the point of the integral point source to the observation point. The number of 吒 method guides, 5, is the heart pressure gradient, the time derivative of the parameter corresponding to the parameter with a small dot on the symbol, the subscript is added as 136, 1 such as 16 is the delay time or elbow time 1.21 for the fixed 1 In order to use the original 13 in the case of the high-pitched Mach number of the rotor, the formula can still be used. In this paper, the fixed surface is selected, and the two are not cylindrical, and the axis coincides with the rotor shaft. The 1 grid point has a uniform interval in the circumference, and the distribution in the vertical direction is concentrated to the rotor plane by the dimension stretching function. The formula for the internal rotation of the rotor for the fixed integral plane is still 2, but In the formula, the 1 and 2 people are simplified, so the formula of 1.1 is changed to 1.2.2. The aerodynamic data is prepared for hovering noise calculation. The aerodynamic data that needs to be prepared is obtained by solving the Euler equation. In order to perform spatial dimension interpolation, it needs to be prepared. All mesh vertex coordinates around a single paddle. ;17.;4, and then find the center coordinates of the grid unit, and also prepare the sound at the corresponding point to divide the integral surface into enough blocks. The parameters on the block are replaced by the center point parameter, then the formula 2 can be turned into OK, but the factory 5 value used is the value of delaying 1 pay 3 Han 1 1 such as 4. The delay time is a crucial concept. The sound signal sent by a sound source point at that moment is just right. When the time reaches the observation point, as long as the factory 5 of the integral surface of the integral surface is known, the sum can be summed and estimated. Out of control integral surface pressure, and sound pressure cascade 5.

The calculation of sound pressure gradient uses the gradient theorem 1.23 to determine the physical parameters on the surface. The high-efficiency interpolation method divides the cylindrical magic surface evenly in the circumferential direction, and distributes the vertical stretching function to the rotor plane in the vertical direction to find the divided The coordinates of the center point of each face, using the one-dimensional linear interpolation to insert the sound pressure and sound pressure gradient value of the center point of the paying panel, the idea of ​​interpolating is to first find the hexahedron containing the interpolated points, 8 of the hexahedron The vertex is the center point of the mesh unit obtained as described above, and then the flow parameters of the interpolated point are obtained by linear interpolation using the flow parameter values ​​at the eight vertices. At the time of interpolation, pay attention to the two points and 1 boundary processing. Because the flow field calculation uses the grid face to steal the toilet, the article withdraws from the 1 crystal net, 4, and the Wei processing method is the processing of the boundary condition when the flow field is calculated. The periodic boundary conditions and the secant boundary conditions are used to supplement the boundary points and the flow parameters of the particles at the boundary. If the boundary has = 2, i = each point is searched for in the center point of all the grids, this will be the time of the normal, and the improvement can be made first to find the hexahedron containing the first inserted point of the surface. The =7=1 point on the integration surface starts and completes the interpolation, then inserts =; = 2 points, at which point it is searched around the last hexahedron without having to search through the whole field. It is worth noting that in order to ensure the continuity of the interpolation, the loop mode also needs to change first, and then the interpolation efficiency is greatly improved from the improved one, and the interpolation time is reduced from the original hours to several tens of seconds. 1.2.4 Calculation of the delay time for the suspended 7 flow field. Selected, paragraph fixed. Also when. The delay time is delayed and engraved. For, observe the moment. = is the radius of radiation and its value is . The value of the bedding value at the delay time of the coordinates of the center point of the surface is determined to be easy to understand. Another auxiliary integration surface that rotates with the rotor is taken. The size and shape of the surface are the same as the fixed integration surface. The time integral of the fixed integration surface and the auxiliary integration surface of the time-history is performed on the fixed integration surface, but the integrand is used as the value of the delay time, and the time is obtained. The parameters of the sound source panel are fixed on each of the fixed integral surface and the auxiliary integrated surface. It is required to call a certain source surface of a certain source surface in the integrand function value such as the inch (1) to find the face element that overlaps the face element and the auxiliary integration surface at the time, and then perform interpolation. The above steps are repeated at the observation point from the beginning of the research, and the use of the above steps. This formula can calculate the noise generated by a cycle as a function of time. 2 Example and analysis of Mu Wencai two paddles 1 spin model 151 for noise, its blade is a plane, no twist, the type is NACA0012, exhibition The chord ratio is 13.7. The radius i of the rotor is 1.045, the chord length is 7.62, and the total angular angle is 0. No lift is used to calculate the noise when the tip Mach number is 0.850.900195. The position of the observation point is 0, 0, 3.0, and the face is taken, IR=1.IOb Court 4, 6 points, and the sound pressure signals of the observation points under three different Mach numbers are compared with the experimental values. It can be seen that the calculated value of 4 experimental values ​​is in accordance with the cluster. The wooden method is used to reflect the change of the sound pressure signal of the far field observation point with time. However, the calculated negative pressure peak and phase have a certain difference from the experimental value. The reason for this is that the Euler equation ignores the effect of stickiness. Only part of the pole noise is taken into account.

And the truncation error in the integral and interpolation; as the Mach number of the tip increases, the peak value of the sound pressure increases sharply. This is due to the non-local enhancement of the flow. The sound pressure value is calculated at 0.90 with the continent 6, = 05 Calculate the sound. 1; The value and the cabinet 7 give the sound pressure of the rotation point observation point of the rotation, and the variation law. Can be seen from the middle of winter. There are two peaks in the rotary rotation of the rotor. And the sound 1 is periodically fluctuating around zero. The qualitative law and theoretical analysis of calculated values.

There is a difference at the peak. When +, =1.2, the calculated value is closest to the experimental value; when and ==1.6, the calculated value deviates farthest from the experimental value. This is due to the influence of the range of the nonlinear region, that is, when 1. soil! 1 When the radius of the surface is too small, it does not contain all the nonlinear regions, and the calculation is not accurate. When the radius of one surface is too large, the accuracy of the nonlinear flow value is not enough, resulting in a large interpolation error, and the calculated sound pressure signal error. The position determination of the integral surface of the larger magical oil control must contain both the nonlinear range of the rotor flow field and the physical quantity such as sound pressure on the control integral surface with sufficient accuracy. After using the high-efficiency interpolation algorithm of this paper, the 0,1殓 required for noise calculation is very very small compared with the time for solving the unsteady 6161 equation. For example, the calculation of a hovering flow solution on 600 volumes is different according to the mesh density. It takes 3 to get and the noise calculation is only about 2.

1;1. The influence of the difference of the position of the lamp surface on the calculation of sound pressure 3 Conclusion The far-field noise of the hovering flow is calculated, and the calculation program for solving the hovering flow noise is developed. The example of the helicopter rotor model is 4, and the method of noise prediction has a good application prospect.

To more accurately simulate helicopter rotor flow, it is more accurate to predict aerodynamic noise. Using the unsteady 5 equation solution to determine the nonlinear region flow parameters and combining it with the formula to solve the aerodynamic noise is a development trend of noise calculation.

Tang Diyi, Li Wenlan, Qiao Yuyang. Aircraft noise basis. Xi'an Northwestern Polytechnical University Press, 1995 Zhu Ziqiang and so on. Apply computational fluid dynamics. Beijing Beijing University of Aeronautics and Astronautics Press, 1998 Wang Liqun. Helicopter rotor flow field 1 equation calculation and noise prediction PhD thesis. Xi'an Northwestern Polytechnical University, 1998, 24 lines or more Papers published in the engineering of the two monthly universities in Singapore for 8 months, the results of the papers in the project Suozhu Monthly are highlighted by the strict selection of the Ministry of Education of Singapore, Northwestern Polytechnical University in 1999 and 2000 respectively 17 The name and 24 freshmen were selected to be sent to the National University of Singapore and Nanyang Technological University for full scholarship studies. The two universities were highlighted by the Engineering Index Monthly during the month from October 2000 to May 2001. Among the 23 famous schools at home and abroad, the two schools were ranked first and third in the number of papers indexed by more than 24 lines in the monthly index of engineering index; the number of the highest number of lines included in the National University of Singapore is ranked first. The 35th line of Nanyang Technological University is 7 rows lower than the MIT MIT. It is only one line lower than the 36th line of Tsinghua University. The two are listed at home and abroad from October 2000 to May 2001. The number of papers and the number of papers included in the monthly index of the famous university index is Harbin Industrial Beijing Aerospace Shanghai Transportation Beijing Nanyang Institute of Technology Xi'an Transportation Hsinchu Transportation Zhejiang Hong Kong Chinese Tsinghua Huazhong Technology Hong Kong Hong Kong Polytechnic Tokyo Industrial China Science and Technology Hsinchu Tsinghua Taiwan Hong Kong Technology Successful Northwest Industrial MIT National Singapore Hong Kong City Beijing Aerospace Beijing Harbin Industry China Science and Technology Huazhong Technology Shanghai Transportation Xi'an Transportation Northwest Industrial Zhejiang Hong Kong Chinese Hsinchu Tsinghua Tsinghua Taiwan Hong Kong Polytechnic Hong Kong Technology Hsinchu Traffic Hong Kong City Tokyo Industrial Success Nanyang Polytechnic National Singapore Massachusetts Institute of Technology

Steel Structures

Steel structures can be used in many industries such as foundation reinforce, electric power transmission structures and tubular scaffolding, etc.

A flange can also be a plate or ring to form a rim at the end of a pipe when fastened to the pipe. A blind flange is a plate for covering or closing the end of a pipe. A flange joint is a connection of pipes, where the connecting pieces have flanges by which the parts are bolted together.

Although the word flange generally refers to the actual raised rim or lip of a fitting, many flanged plumbing fittings are themselves known as 'flanges':

There are many different flange standards to be found worldwide. To allow easy functionality and interchangeability, these are designed to have standardised dimensions. Common world standards include ASA/ASME (USA), PN/DIN (European), BS10 (British/Australian), and JIS/KS (Japanese/Korean). In the USA, ANSI stopped publishing B16.5 in 1996, and the standard is ASME B16.5

Steel Structures,Steel Structure Building,Classic Steel Structure,Light Steel Structures

Yixing Steel Pole International Trading Co., Ltd , https://www.yx-steelpole.com