Implicit large-eddy simulation of an over-expanded screeching rectangular jet is performed with a seventh-order finite difference scheme.Good agreement is found between the predicted flow-and acoustic fields with the ...Implicit large-eddy simulation of an over-expanded screeching rectangular jet is performed with a seventh-order finite difference scheme.Good agreement is found between the predicted flow-and acoustic fields with the experimental observations.Fourier decomposition,phase-averaging analysis and Spectral Proper Orthogonal Decomposition(SPOD)are used to investigate the origin of the screech,the shock leakage during the shear-layer flapping,and the distinguishing fluctuating characteristics in the minor-and major-axis plane of the rectangular jet.It finds that the screech is radiated from the end of the forth shock cell,where the interaction of the shock waves with the shear layer causes periodic leakages of shock-wave tips in the minor-axis plane,resulting in the generation of intense acoustic waves in the surrounding air.An obvious flapping mode at the same frequency of the screech is captured in the minor-axis plane and dominates the dynamic motions of the rectangular jet.The SPOD modes of pressure and velocity fluctuations at the screech frequency help to reveal the relationship between the screech generation and the coherent structures.展开更多
To achieve high parallel efficiency for the global MASNUM surface wave model, the algorithm of an irregular quasirectangular domain decomposition and related serializing of calculating points and data exchanging schem...To achieve high parallel efficiency for the global MASNUM surface wave model, the algorithm of an irregular quasirectangular domain decomposition and related serializing of calculating points and data exchanging schemes are developed and conducted, based on the environment of Message Passing Interface(MPI). The new parallel version of the surface wave model is tested for parallel computing on the platform of the Sunway BlueLight supercomputer in the National Supercomputing Center in Jinan. The testing involves four horizontal resolutions, which are 1°×1°,(1/2)°×(1/2)°,(1/4)°×(1/4)°, and(1/8)°×(1/8)°. These tests are performed without data Input/Output(IO) and the maximum amount of processors used in these tests reaches to 131072. The testing results show that the computing speeds of the model with different resolutions are all increased with the increasing of numbers of processors. When the number of processors is four times that of the base processor number, the parallel efficiencies of all resolutions are greater than 80%. When the number of processors is eight times that of the base processor number, the parallel efficiency of tests with resolutions of 1°×1°,(1/2)°×(1/2)° and(1/4)°×(1/4)° is greater than 80%, and it is 62% for the test with a resolution of(1/8)°×(1/8)° using 131072 processors, which is the nearly all processors of Sunway BlueLight. When the processor's number is 24 times that of the base processor number, the parallel efficiencies for tests with resolutions of 1°×1°,(1/2)°×(1/2)°, and(1/4)°×(1/4)° are 72%, 62%, and 38%, respectively. The speedup and parallel efficiency indicate that the irregular quasi-rectangular domain decomposition and serialization schemes lead to high parallel efficiency and good scalability for a global numerical wave model.展开更多
The environment modeling algorithm named rectangular decomposition, which is composed of cellular nodes and interleaving networks, is proposed. The principle of environment modeling is to divide the environment into i...The environment modeling algorithm named rectangular decomposition, which is composed of cellular nodes and interleaving networks, is proposed. The principle of environment modeling is to divide the environment into individual square sub-areas. Each sub-area is orientated by the central point of the sub-areas called a node. The rectangular map based on the square map can enlarge the square area side size to increase the coverage efficiency in the case of there being an adjacent obstacle. Based on this algorithm, a new coverage algorithm, which includes global path planning and local path planning, is introduced. In the global path planning, uncovered subspaces are found by using a special rule. A one-dimensional array P, which is used to obtain the searching priority of node in every direction, is defined as the search rule. The array P includes the condition of coverage towards the adjacent cells, the condition of connectivity and the priorities defined by the user in all eight directions. In the local path planning, every sub-area is covered by using template models according to the shape of the environment. The simulation experiments show that the coverage algorithm is simple, efficient and adapted for complex two- dimensional environments.展开更多
Similar to Auld's solution for Lamb waves,the wave modes in elastic rectangular bar are solved by partial wave decomposition method.The partial waves are composed of plate modes with the same wavenumber component ...Similar to Auld's solution for Lamb waves,the wave modes in elastic rectangular bar are solved by partial wave decomposition method.The partial waves are composed of plate modes with the same wavenumber component in waveguide longitudinal direction,thus free boundary conditions on one pair of opposite surfaces are automatically satisfied.Based on completeness assumption and orthogonality of the plate modes,four independent eigenequations are eventually derived for dispersion curve and mode shape investigation.Numerical evaluation shows the calculated results are in consistent with the FEM results.It is then verified that the plate modes which obliquely bounced back and forth between the two opposite surfaces compose the guided modes traveling in the rectangular waveguides with certain wave numbers in transversely resonant cases.展开更多
A fast Cholesky decomposition and a fast inverse Cholesky decomposition method for A T A are presented,where A is an m×n rectangular Toeplitz block matrix,we give the FCD algorithm for computing...A fast Cholesky decomposition and a fast inverse Cholesky decomposition method for A T A are presented,where A is an m×n rectangular Toeplitz block matrix,we give the FCD algorithm for computing R , and the FICD algorithm for computing R -1 ,both allow for an efficient parallel implementation,for solving a least squares problem and require only O(mn) operations.展开更多
基金support of the National Natural Science Foundation of China(No.12372221)is acknowledged。
文摘Implicit large-eddy simulation of an over-expanded screeching rectangular jet is performed with a seventh-order finite difference scheme.Good agreement is found between the predicted flow-and acoustic fields with the experimental observations.Fourier decomposition,phase-averaging analysis and Spectral Proper Orthogonal Decomposition(SPOD)are used to investigate the origin of the screech,the shock leakage during the shear-layer flapping,and the distinguishing fluctuating characteristics in the minor-and major-axis plane of the rectangular jet.It finds that the screech is radiated from the end of the forth shock cell,where the interaction of the shock waves with the shear layer causes periodic leakages of shock-wave tips in the minor-axis plane,resulting in the generation of intense acoustic waves in the surrounding air.An obvious flapping mode at the same frequency of the screech is captured in the minor-axis plane and dominates the dynamic motions of the rectangular jet.The SPOD modes of pressure and velocity fluctuations at the screech frequency help to reveal the relationship between the screech generation and the coherent structures.
基金supported by National Basic Research Program of China (Grant Nos. 2010CB950300, 2010CB950500)Public Science and Technology Research Funds Projects of Ocean (Grant No. 201105019)+1 种基金Key Supercomputing Science-Technology Project of Shandong Province of China (Grant No. 2011YD01107)Scientific Research Foundation of the First Institute of Oceanography, State Oceanic Administration (Grant No. GY02-2010G22)
文摘To achieve high parallel efficiency for the global MASNUM surface wave model, the algorithm of an irregular quasirectangular domain decomposition and related serializing of calculating points and data exchanging schemes are developed and conducted, based on the environment of Message Passing Interface(MPI). The new parallel version of the surface wave model is tested for parallel computing on the platform of the Sunway BlueLight supercomputer in the National Supercomputing Center in Jinan. The testing involves four horizontal resolutions, which are 1°×1°,(1/2)°×(1/2)°,(1/4)°×(1/4)°, and(1/8)°×(1/8)°. These tests are performed without data Input/Output(IO) and the maximum amount of processors used in these tests reaches to 131072. The testing results show that the computing speeds of the model with different resolutions are all increased with the increasing of numbers of processors. When the number of processors is four times that of the base processor number, the parallel efficiencies of all resolutions are greater than 80%. When the number of processors is eight times that of the base processor number, the parallel efficiency of tests with resolutions of 1°×1°,(1/2)°×(1/2)° and(1/4)°×(1/4)° is greater than 80%, and it is 62% for the test with a resolution of(1/8)°×(1/8)° using 131072 processors, which is the nearly all processors of Sunway BlueLight. When the processor's number is 24 times that of the base processor number, the parallel efficiencies for tests with resolutions of 1°×1°,(1/2)°×(1/2)°, and(1/4)°×(1/4)° are 72%, 62%, and 38%, respectively. The speedup and parallel efficiency indicate that the irregular quasi-rectangular domain decomposition and serialization schemes lead to high parallel efficiency and good scalability for a global numerical wave model.
基金The National Natural Science Foundation of China(No.50475076)the National High Technology Research and Development Pro-gram of China(863Program)(No.2006AA04Z234)
文摘The environment modeling algorithm named rectangular decomposition, which is composed of cellular nodes and interleaving networks, is proposed. The principle of environment modeling is to divide the environment into individual square sub-areas. Each sub-area is orientated by the central point of the sub-areas called a node. The rectangular map based on the square map can enlarge the square area side size to increase the coverage efficiency in the case of there being an adjacent obstacle. Based on this algorithm, a new coverage algorithm, which includes global path planning and local path planning, is introduced. In the global path planning, uncovered subspaces are found by using a special rule. A one-dimensional array P, which is used to obtain the searching priority of node in every direction, is defined as the search rule. The array P includes the condition of coverage towards the adjacent cells, the condition of connectivity and the priorities defined by the user in all eight directions. In the local path planning, every sub-area is covered by using template models according to the shape of the environment. The simulation experiments show that the coverage algorithm is simple, efficient and adapted for complex two- dimensional environments.
基金supported by the National Natural Science Foundation of China(11204227,11674207,11774212)
文摘Similar to Auld's solution for Lamb waves,the wave modes in elastic rectangular bar are solved by partial wave decomposition method.The partial waves are composed of plate modes with the same wavenumber component in waveguide longitudinal direction,thus free boundary conditions on one pair of opposite surfaces are automatically satisfied.Based on completeness assumption and orthogonality of the plate modes,four independent eigenequations are eventually derived for dispersion curve and mode shape investigation.Numerical evaluation shows the calculated results are in consistent with the FEM results.It is then verified that the plate modes which obliquely bounced back and forth between the two opposite surfaces compose the guided modes traveling in the rectangular waveguides with certain wave numbers in transversely resonant cases.
文摘A fast Cholesky decomposition and a fast inverse Cholesky decomposition method for A T A are presented,where A is an m×n rectangular Toeplitz block matrix,we give the FCD algorithm for computing R , and the FICD algorithm for computing R -1 ,both allow for an efficient parallel implementation,for solving a least squares problem and require only O(mn) operations.
