TRANSONIC FLOW CALCULATION OF EULER EQUATIONS BY IMPLICIT ITERATING SCHEME WITH FLUX SPLITTING

Three dimensional Euler equations are solved in the finite volume form with van Leer's flux vector splitting technique. Block matrix is inverted by Gauss-Seidel iteration in two dimensional plane while strongly implicit alternating sweeping is implemented in the direction of the third dimension. Very rapid convergence rate is obtained with CFL number reaching the order of 100. The memory resources can be greatly saved too. It is verified that the reflection boundary condition can not be used with flux vector splitting since it will produce too large numerical dissipation. The computed flow fields agree well with experimental results. Only one or two grid points are there within the shock transition zone.

A Semi-Analytical Potential Solution for Wave Resonance in Gap Between Floating Box and Vertical Wall

Based on potential flow theory, a dissipative semi-analytical solution is developed for the wave resonance in the narrow gap between a fixed floating box and a vertical wall by using velocity potential decompositions and matched eigenfunction expansions. The energy dissipation near the box is modelled in the potential flow solution by introducing a quadratic pressure loss condition on the gap entrance. Such a treatment is inspired by the classical local head loss formula for the sudden change of cross section in channel flow, where the energy dissipation is assumed to be proportional to the square of local velocity for high Reynolds number flows. The dimensionless energy loss coefficient is calibrated based on experimental data. And it is found to be insensitive to the incident wave height and wave frequency. With the calibrated energy loss coefficient, the resonant wave height in gap and the reflection coefficient are calculated by the present dissipative semi-analytical solution. The predictions are in good agreement with experimental data. Case studies suggest that the maximum relative energy dissipation occurs near the resonant frequency, which leads to the minimum reflection coefficient. The horizontal wave forces on the box and the vertical wall attain also maximum values near the resonant frequency, while the vertical wave force on the box decreases abruptly there to a small value.

Iterative analytical solution for wave reflection by a multichamber partially perforated caisson breakwater

This study examines wave reflection by a multi-chamber partially perforated caisson breakwater based on potential theory.A quadratic pressure drop boundary condition at perforated walls is adopted,which can well consider the effect of wave height on the wave dissipation by perforated walls.The matched eigenfunction expansions with iterative calculations are applied to develop an analytical solution for the present problem.The convergences of both the iterative calculations and the series solution itself are confirmed to be satisfactory.The calculation results of the present analytical solution are in excellent agreement with the numerical results of a multi-domain boundary element solution.Also,the predictions by the present solution are in reasonable agreement with experimental data in literature.Major factors that affect the reflection coefficient of the perforated caisson breakwater are examined by calculation examples.The analysis results show that the multi-chamber perforated caisson breakwater has a better wave energy dissipation function(lower reflection coefficient)than the single-chamber type over a broad range of wave frequency and may perform better if the perforated walls have larger porosities.When the porosities of the perforated walls decrease along the incident wave direction,the perforated caisson breakwater can achieve a lower reflection coefficient.The present analytical solution is simple and reliable,and it can be used as an efficient tool for analyzing the hydrodynamic performance of perforated breakwaters in preliminary engineering design.

Experimental study on wheeled vehicle hydro-pneumatic suspension fault detection

A four-channel MTS road simulation system,which is used to regenerate the acceleration signal at the axle head is presented. A new fault detection method is proposed,which is based on the remote parameter control（ RPC） technology for vehicle hydro-pneumatic suspension system. The transfer function between the drive signals and the axle head acceleration should be identified before the RPC iterative calculation on a computer. By contrasting with the desired frequency response functions（ FRF）,excited through the sample spectrum of road,the iterative convergence speed of the drive function and weighted error are used to detect faults existing in the vehicle＇s suspension. Experimental results show that during the process of regeneration of the acceleration signal at the axle head,the characteristics of failure of the hydro-pneumatic spring are changed randomly resulting in a dramatic increase in calculation of the RPC iterative,which enables relatively large iterative convergence errors. This method can quickly detect and locate a suspension fault and is a simple bench test way in suspension fault detection.

An Iterative Calculating Method for Inbreeding and Relationship Coefficient

The iterative formulas of inbreeding and relationship coefficients were put forward by using numerator elationship. It is suitable for any none - generation - overlap pedigree. The inbreeding and relationship coeffi- ient of offsprings can be calculated by those of parents. The deducing process of numerator relationship is simple and clear comparing with path analysis. An example shows the usage of these formulas.

Algorithm of Slub Yarn Parameter Measurement Based on Capacitive Sensors

A new algorithm of measurement slub yarn parameter was put forward to improve precision and efficient. The basic principal of measurement slub yarn by parallel-plate capacitor was introduced,and slub yarns were tested with a measurement system developed by ourselves. Time sequence for slub length and slub space can be got. And distributions of slub length,slub space and slub scaling factor can also be obtained. The agreement can be attained compared with those original settings. Some error was analyzed also. Consequently this system is effective,and can be adopted in practice.

Scour Development Around Submarine Pipelines due to Current Based on the Maximum Entropy Theory

This paper presents the results from laboratory experiments and theoretical analysis to investigate the development of scour around submarine pipeline under steady current conditions. Experiments show that the scour process takes place in two stages: the initial rapid scour and the subsequent gradual scour development stage. An empirical formula for calculating the equilibrium scour depth(the maximum scour depth) is developed by using the regression method. This formula together with the maximum entropy theory can be applied to establish a formula to predict the scour process for given water depth, diameter of pipeline and flow velocity. Good agreement between the predicted and measured scour depth is obtained.

Prediction method of impeller performance and analysis of loss mechanism for mixed-flow pump

A loss model for the mixed-flow pump impellers was developed by summarizing a variety of loss calculation formulas systematically.The internal flow field of the impeller was obtained by employing the iterative calculation for S 1 and S 2 stream surfaces to solve the continuity and motion equations of fluid.Based on the calculation method of the flow field and the loss model,it is achieved to predict the impeller performance of the mixed-flow pump and the performance curves of a mixed-flow pump model with adjustable blades.Compared with the test data,the loss model of the mixed-flow pump based on the iterative calculation can predict the impeller performance quickly and accurately,which has a high value on the engineering applications.Based on the test verification,curves of various kinds of losses varied for the flow rate were analyzed under different blade angles.In addition,the mechanisms of various kinds of losses inside the mixed-flow pump impeller were discussed in-depth.