Applied Mechanics and Materials Vol. 389

Abstract: In general, marine propellers have complicated geometries and as a consequence complicated flow around propeller. The aim of this work is to find an appropriate method and assess the turbulence model to approach the open water hydrodynamic characteristics of the marine propellers. In this work, a numerical modeling using a finite volume commercial code (FVM) for different turbulence models has been applied on the well known conventional screw propeller DTRC P4119. The 3-D solid model of P4119 is established using pro/E software and for the mesh generation ANSYS-ICEM has been used. Steady Reynolds-Averaged Navier Stokes (RANS) simulations are accomplished using FLUENT software with unstructured mesh in the rotating computational domain and structured mesh for the rest of the domain. The open water performance coefficients, thrust (K_T), torque (K_Q) and efficiency (η) have been calculated and compared with available experimental data to assess the applicability of different turbulence models for the open water study of propeller. This paper shows that, the accuracy of the CFD based on RANS equations is dependent on the used turbulence model and the RNG K-epsilon turbulence model yields to provide the most accurate results. Also, all the turbulence models via FLUENT software behave the same behavior for the total span of the advance coefficient (J) with two types of result accuracy. All the turbulence models shows high accuracy at low advance coefficient and this accuracy decreases but with an acceptable error till it decreases suddenly at the maximum advance coefficient.

Abstract: This paper analyzes the technology based on the PDM ship parallel collaborative design, studies the features of ship parallel collaborative design, describes the application of distributed database in the ship parallel collaborative design project.

Abstract: 3D Electro Magnetic Compatibility (EMC) Scanning system is based on a spectrum analyzer as the core, can provide the relevant parameters of the EMC quickly and accurately, and can be a single component, PCB, machine, cable-round three-dimensional test. Through the host computer, it can realize the visualization of electromagnetic radiation to show real state of electromagnetic radiation.

Abstract: The circumferential overlap trisection helical baffle shell-and-tube heat exchanger (cothSTHX) is a modification one based on the quadrant helical baffle one to improve the heat transfer performance. The model of cothSTHX has 34 tubes and 3 rods with tube layout of equilateral triangle and a baffle inclined angle of 20°, and the numerical simulation of flow and thermal performances was conducted using the commercial CFD software FLUENT. The distributions of temperature, pressure and velocity, and temperature, pressure or velocity nephograms with superimposed velocity vectors for special slices can provide access to important implicit information in the simulation results. The Dean vortex secondary flow, which is one of the key mechanisms of enhancing heat transfer in heat exchangers, is clearly depicted, and it shows that the fluid in spiral channel flows outward under the centrifugal force, then flows back to the axis under radial differential pressure, thus a single vortex is formed in each baffle pitch cycle. The unfolded concentric hexagonal slices are designed to make up for the defect that the shortcut leakage flow in the V-notch zone of the adjacent baffles could not be depicted along the longitudinal slices. Moreover, the shortcut leakage flow is restricted with the damper effect of the structure that a row of tubes in the circumferential overlap area of adjacent baffles.

Abstract: Traditional collaborative filtering recommendation system put emphasis on data but ignores the users. The recommendation of the similarity analysis emphasizing too much from the data perspective lacks depth analysis of the users without regarding the similarity from the users perspective. In this paper, user character is introduced to improve the user model, and two character-based collaborative filtering recommendations will be proposed: one is to compute user similarity from the user character perspective and select nearest neighbor, and then generates recommendation; another is based on the character-item rating matrix, and then make recommendation to the prospective users. These two ideas can well make up for the inadequacies of the current collaborative filtering recommendation system.

Abstract: Based on open source embedded operating system uClinux, embedded applications system taking ARM microprocessor as the core was connected with Internet. Through embedding Web server to the ARM embedded system functions and adding embedded Gateway Interface CGI program, the interactive delivery with the long-distance customers Web browser order and response information come true.

Abstract: A method of measuring wavefront distortion field is presented in this paper, which gets the OPD through measuring deviation displacement field induced by the beams from center of camera to the mark points crossing the flow field. The experiments of a trans-aerosphere vehicle model in 2 meter supersonic tunnel have demonstrated that the method of this paper can be used to measure the large field of wavefront distortion, and the structures of wavefront distortion generated by oblique shock waves of the vehicles head and wing are correct. This method is simple and provides a new way to measure and observe aero-optics phenomena.

Abstract: According to the plastic floor assumptions, the floor pressure distribution law was obtained based on plane force analysis of hydraulic support. In order to compare the floor pressure on the elastic floor and plastic floor, Elastic foundation beam theory was introduced to the calculation of the floor pressure. The results show that the pressure distribution is changed with the changing of the subgrade coefficient. The pressure is trapezoidal distributed when the floor is relatively soft and the plastic floor assumptions is reasonable. In a relatively hard rock floor, the maximum pressure appear near the column nest which is very different from the calculation results based on the plastic base plate assumptions. It is suggested that the soft and the hard rock floor should be treated differently during the design and selection of hydraulic support. .

Abstract: Cost controlling is key behavior of getting more profits in an enterprise, but the cost of construction material cover 40-60 percent or more. So, reduce its cost as less possible as on the premise of insuring material quality is very important. The article starts from this, and gives some suggestions about controlling of the cost of construction material.

Abstract: According to the design criteria referred to CCAR-25,the static strengths of accessorial equipments (single stretcher-supporting equipment, double layer stretcher-supporting equipment and nursing-type unit) and the track-mounting mechanism applied to fix the accessorial equipments to the seat tracks of the airliner are analyzed under five loads by using the software MSC.PATRAN. Based on the analysis results, the strengths of the accessorial equipments will be checked, the structures can satisfy the requirements of strength.