Study of the Lift Force Induced by An Interceptor on A High-Speed Mono-Hull:The Affecting Factors and Estimation Formula

To find a better way to estimate the lift force induced by an interceptor on a high-speed mono-hull ship,a series of high-speed mono-hull ship models are designed and investigated under different conditions.Different lift forces are obtained by numerical calculations and validated by a model test in a towing tank.The factors that influence the force are the interceptor height,velocity,draft,and deadrise angle.The relationship between each factor and the induced lift force is investigated and obtained.We found that the induced lift mainly depends on the interceptor height and advancing velocity,and is proportional to the square of the interceptor height and velocity.The results also showed that the effects of the draft and deadrise angle are relatively less important,and the relationship between the induced lift and these two factors is generally linear.Based on the results,a formula including the combined effect of all factors used to estimate the lift force induced by the interceptor is developed based on systematic analysis.The proposed formula could be used to estimate the lift force induced by interceptors,especially under high-speed condition.

Aerodynamic Effects on TLP Type Wind Turbines and Predictions of the Electricity They Generate

This research proposes a new offshore wind energy generation system that uses a tension leg platform (TLP) and describes experiments performed on a TLP type wind turbine in both waves and wind. The following conclusions can be made from the results of this research. 1) In the case of coexisting wave-wind fields, the wind effect stabilizes the pitch motion. 2) The wind effect decreases vibration of the mooring lines when waves and wind coexist. In particular, the springing (2nd or 3rd order force) also decreases in this field. 3) It can be estimated that the reduction in the rate of generation of electrical power can be up to about 6% as a result of the heel angle. In addition, the annual amount of electricity generated was estimated along with the utilization factor based on the experimental results.

Performance analysis of a tuned point absorber using SPH calm water and wave tank simulations

In this paper,two smoothed particle hydrodynamics(SPH)models,namely SPH-W and SPH-C were used to evaluate the motion response of a point absorber wave energy converter(WEC).In the SPH-W model,a long wave flume was constructed and a long simulation was performed to obtain the motion response of the WEC.In the SPH-C model,the SPH method is only used to find the hydrodynamic coefficients of the device by analysing a few seconds of free-decaying motion of WEC in calm water in a much smaller numerical flume.Then,these coefficients were inserted in the equation of motion of a heaving WEC that was solved using a 4th order Runge-Kutta(ODE45)solver in MATLAB.First,the energy conservation property of the WCSPH model was examined through a standing wave benchmark test.Then,the wavepoint absorber interaction was simulated.While the simulation time for SPH-C model is much smaller than that of SPH-W,it gave almost similar results for the motion response of WEC.These two models were used to evaluate the effects of the control force and the draft of a cone-cylinder point absorber on its hydrodynamic responses.The results showed that compared to the effect of the supplementary inertia,changes in the draft of the WEC have a small influence on its hydrodynamic responses.The buoy draft has an inverse relationship with both added mass and damping coefficients.However,increasing the supplementary mass increases the added mass and decreases the hydrodynamic damping coefficients.

Numerical and experimental analyses of hydrodynamic performance of a channel type planing trimaran

This paper studies the hydrodynamic performance of a channel type planing trimaran. A numerical simulation is carried out based on a RANS-VOF solver to analyze the hydrodynamic performance of the channel type planing trimaran. A series of hydrodynamic experiments in towing tank were carried out, in which both the running attitude and the resistance performance of the trimaran model were recorded. Some hydrodynamic characteristics of the channel type planning trimaran are shown by the results. Firstly, the resistance declines significantly, with the forward speed across the high-speed resistance peak due to the combined effects of the aerodynamic and hydrodynamic lifts. Secondly, the resistance performance is influenced markedly by the longitudinal positio- ns of centre of the gravity and the displacements. Besides, the pressure distribution on the hull and the two-phase flow in the channel are discussed in the numerical simulations.

A numerical study of passenger side airbag deployment based on arbitrary Lagrangian-eulerian method

The passenger side airbags(PAB)are usually larger than the driver airbags.Therefore,the inflator of PAB is more powerful with high mass rate.In this paper,an Arbitrary Lagrangian-Eulerian(ALE)method based computational method is developed to simulate the deployment of a PAB.The tank test is used to test the property of the inflator.Through comparison of numerical and experimental results,the ALE method is validated.Based on a failed airbag test,a smaller sub-airbag is placed inside PAB to disperse the gas flow to directions which are less damaging.By applying dynamic relaxation,the initial mesh corresponding to the experimental terms is obtained.The results indicate that the interior pressure and impact force coincide with the test data,and the method in this paper is capable of capturing airbag deploying process of the PAB module accurately.

THE NATURAL CONVECTION OF AQUIFERS WITH CONSTANT HEAT SOURCES AND ITS INFLUENCE ON TEMPERATURE FIELDS

By combining sand tank tests with numerical simulations, this paper studies the temperature fields around constant heat sources to reveal the mechanism of the natural convection and its influence on the temperature fields in the process of energy storage. Using the ＂24-channel temperature auto acquisition system＂ developed by our research group in the tests, the temperatures are recorded at measuring points within the research area in the tests, the revised Brinkman equation and a transfer-convection balance model are used for solving the aquifer water-thermal coupling problems, and through comparison of the test results with the calcula- tion results, it is discovered that the influence ranges and the variations of the two temperature fields are consistent, which validates the mathematical model. On the basis of this, we also study the influences of the heat source positions and the boundary conditions on the temperature fields, and the results show that, under the natural convection, the heat source positions may influence the distri- bution of the temperature fields, thus affect the energy storage. For the same energy storage layer, the temperature field for the top energy storage is characterized by a smaller heat influence range and a relatively concentrated temperature distribution. However, when the heat source is at the bottom, the range of a temperature field, and the temperature is relatively dispersed, which is not favorable to heat recycle, with the same heat source position, the boundary conditions determine the size of the critical Rayleigh number, and thus have an influence on the occurrence and the strength of the natural convection, and accordingly, on the temperature fields.