Applied Mechanics and Materials Vols. 246-247

Abstract: It is inevitable that the wake affects on the braking force of tugboat towing in the stern of a ship. In order to understand the effect of ship-tugboat interaction on the braking force of tugboat, we have to consider two interference components, namely on the tugboat’s braking force in ships wake and on ship’s hull resistance. First, the interference component on the tugboat’s braking force is predicted considering the scale effect of ship’s wake velocity distribution, and using the braking force coefficient of tugboat-self in the uniform flow[1]. Then the interference component on ship’s hull resistance is also estimated under an assumption, which this component in full scale ship is in proportion to Schlichting’s frictional resistance as the component obtained in scale model experiments being a constant. Finally, the effective braking force for full scale tugboats was predicted by using the experiment data and the assumptions mentioned above.

Abstract: Unstable motion is characteristics of tugboat for retarding a large vessel. It will make the capabilities of tugboat’s braking force vary. In this paper, we used an ASD-tugboat model to measure the yaw and sway amplitudes and the braking force when the tugboat model is towing on a line. In addition, we still had carried out the tests of hydrodynamic forces acting on the tugboat model. Finally, we confirmed that the yaw and sway motion was existed and the tugboat’s braking performance was affected by the unstable motion.

Abstract: By the method of computational fluid dynamics (CFD), this paper calculates the aerodynamic parameters of one complex high-speed train model which adopts different support forms when the reference velocity is 70m/s under different operating conditions. It also analyses the support interference mechanism from the point of flow field structure. The results show that the distributed cylinder support form causes least interference on the model, while the single big cylinder support forms change the flow field structures much which leads to much change of the aerodynamic parameters of the model. The distributed cylinder support form can be applied as a good support form for the high-speed train wind tunnel tests.

Abstract: The implementation of bridge blasting process for ground burst unit of Corps Engineers is complex with lots of impact factors, and it is difficult to determine the blasting program. In order to better solve the problem, the author in this paper proposes a new assessing approach of bridge blasting program based on combination of intuitionist fuzzy set theory and TPOSIS, and defines the optimal solution as well as worst solution of intuitionist fuzzy concept, building the evaluation index system of bridge blasting program majors in blasting target, the implementation staff for blasting, blasting tools and equipments. In this way, the author establishes the model of corps engineers of bridge blasting program based on intuitionist fuzzy sets and TOPSIS method, and verifies the model through the use of instances to prove the feasibility and effectiveness of the model with this method.

Abstract: According to many researches, the presence of stress-sensitivity has been confirmed in reservoir rocks. Because it will create huge damage to the permeability of reservoirs, sufficient attention should be made. In this paper, through the experiment, the permeability value change with effective pressure in the condition of saturated with irreducible water and dry environment were compared. The study showed that the stress-sensitivity of core sample was more obvious in the condition of saturated with irreducible water.

Abstract: Since the propulsion performance of fish pectoral fin is directly related to its kinematic parameters, for improving the propulsion performance of pectoral fin, the kinematic model of propulsion motion of pectoral fin was established, the hydrodynamic force acted on the pectoral fin during propulsion motion was calculated and the mathematic model which optimized the propulsion performance of pectoral fin was established. Then MATLAB was used to write the genetic algorithm program which is used to get the optimal solution of kinematic parameters of pectoral fin. Finally, the simulation analysis of the propulsion performance of pectoral fin was developed. From the simulation result, it can be got that the optimal model established and the optimal algorithm adopted can play an important role in improving the propulsion performance of pectoral fin. Therefore, the optimal analysis developed in this paper is reasonable and effective as well as provides theoretical reference to the research on the bionic pectoral fin and the new underwater maneuvering vehicle.

Abstract: In this paper, we make a research on the dynamic characteristics of a sphere material, mainly using golf as an example. Golf is composed of such as poly butadiene rubber or other synthetic rubber, ion resin, etc. and different viscoelastic materials. The viscoelastic characteristics of this material are selected as spectrometer for evaluation. However, the impact performance of the golf course materials cannot pass such a test to assess, because golf have great impact on the deformation and high strain rate viscoelastic spectrometer. On the other hand, the impact properties of the metal can be used to assess the split Hopkinson pressure bar. However, the rod is not suitable to be used to evaluate the strain wave interference and noise propagation in the impact properties of the polymer materials. Therefore, the split Hopkinson pressure bar has been modified to make it more applicable to the valuation of the polymer materials. The article is based on the concept of modified split Hopkinson pressure bar to make the golf impact evaluation of the performance materials.

Abstract: High speed torque is very important in tennis batting process , this paper discusses the shoulder and torso rotation torque generated by the weight of tennis sports influence. Taking 48 tennis players as research objects, the rotation torque of professional tennis players are relatively outstanding with performance value,so we concluded that in the case of keeping the torso erect and through the process optimization of the rotation, we could combined shoulder movement and body bottom-up movement. These results suggested that some given hitting model can not only increase the performance of the tennis player on the pitch, but also reduce the risk of causing excessive damage.

Abstract: As the number of the urban population attains a continuous increasing these years, the carrying load of all kinds of transportation lines in society changes into heavier as well. For the purpose of fulfilling the services demands of the rail transportation, the elevated station has turned into a new type of transportation structure, and exercises a critical role in the reduction of the social transportation pressure. The elevated station is a body integrated by both the rail transportation and the elevated bridge, and is much stronger than the traditional structural model in the aspects of the carrying load and structure performance. In accordance with this point, the author emphatically analyzes the structural dynamics of the elevated station in rail transportation in this paper, with the purpose of bringing the using performance of the elevated station into better play.

Abstract: The forecasting precision of short-term wind speed is not high for its chaos and time-varying. Aimed at the problem, the novel data space is reconstructed with the best embedding dimension and time delay according to the phase space reconstruction. On the basis, neural network (NN) is used as the modeling tool with the novel sample data. Meanwhile, the structure of NN is confirmed compared with the others on the precision. In the end, the model of short-term wind speed is able to be obtained. The results show that the method is available and the Mean absolute error (MAE) is decreased to 16.2% for 2 hours.