Applied Mechanics and Materials Vols. 275-277

Abstract: For shielding radio frequency and electromagnetic interference, the sealed case is usually used for airborne electronic equipment. As electronic products become faster and incorporate greater functionality, their thermal characters must be well analyzed and designed. Three-dimensional thermal numerical simulations from inside to outside of the sealed case were performed to get a clear sight of the coupling heat transfer in conduction, natural convection, and radiation. Temperature field, fluid flow field, and local heat transfer coefficient layout outside the wall were got, which were compared with the outcomes of the empirical method. The results of numerical simulation showed that in sealed case conduction was the dominant way, and natural convection had the comparative ratio with radiation, both of them were less than 25%. The maximum error of no radiation including could get to 43.2%.

Abstract: An analytical solution for pressure-driven electrokinetic flows in a narrow capillary is presented based on the Poisson–Boltzmann equation for electrical double layer and the Navier–Stokes equations for incompressible viscous fluid. The analytical solutions indicate that pressure-driven flow of an electrolyte solution in microchannel with charged solid wall induces a streaming potential, which is proportional to the flowrate and induces an electroviscous effect on flow. A device for measuring the electrokinetic flow rate and streaming potential is proposed.

Abstract: In the evaporative condenser, the shape and structure of the nozzle determines the spraying effect, which affects the overall heat transfer performance of the evaporative condenser. Due to the constraints of its structure, spraying test is difficult in evaporative condenser operation process. The performance of the two types of nozzle spray is simulated by CFD numerical calculation software, using the two-dimensional modeling. The results show that the two-tier shunt platform nozzle sprays more uniformly, the movement of airflow around is relative more regular, the performance of spraying water is more stable. The reference is provided to select the optimal structure of the nozzle under certain conditions.

Abstract: Micro-positive pressure distillation is commonly used in processes where the feed stock or products are oxygen sensitive. Constant column pressure is critical for such process as pressure fluctuations may change column performance and the oxygen-free environment leading to dramatic change in product quality. In this paper, an inert current system designed for micro-positive pressure distillation is introduced. Details of both the operation principle and system features including response time and pressure deviation are studied. Four mathematical equations describing the features are put forward to help select the appropriate parameter. This system is promising for its high sensitivity and simple construction.

Abstract: In order to analyze the influence of the rear wing of a competition race car on the aerodynamics of the whole vehicle, computational fluid dynamics simulations have been performed. Rear wing is set by two elements, a main plate and a flap. Their relative position and the angle of attack of these elements influence the aero- performances in terms of downforce and drag generated; 12 different configurations have been generated, modifying the angle of attack and the slot gap. 3D mesh has been generated from the geometrical model of the vehicle, and air flow around the vehicle and on the rear wing has been evaluated through a CFD commercial software. It has been proved that steeper angles of attack of the mainplate and of the flap contribute to generate more downforce until a certain point; when angle of attack reaches a critical value, the downforce no longer increases and the drag still keep high values.

Abstract: In this study, a computational fluid dynamics (CFD) study based on a finite element method (FEM) was performed for the human aorta with four different flow time patterns (healthy to full intra-aorta pump support). Fully coupled fluid-solid interaction (FSI) simulation was used to investigate the flow profiles in the aortic arch and its branches where the maximum disturbed and non-uniform flow patterns, and the wall shear stress profiles on the same areas. The blood flow was assumed as a homogeneous, incompressible, and Newtonian fluid flow. Flow across four inlets of aortas was derived from a lumped parameter model (LPM). The inlet flow rate waveforms were divided by different blood assist index (BAI), and were calculated with the physiological information of a heart failure patient.

Abstract: Taylor series numerical method (TSNM) is extended to the field of transient heat conduction. Theoretical description of TSNM for transient heat conduction problems is presented. Furthermore, the algorithm is realized and embedded in commercial software ANSYS®. If a lumped mass heat capacity matrix provided, the governing equation of transient heat conduction problems, which is a differential equation, will be solved by a series of recursion calculation of Taylor expanding coefficients. A typical transient heat conduction problem with analytical solution was discussed to verify the TSNM. At last, the TSNM is applied in the transient heat analysis of an all-solid fiber optic gyro (FOG).

Abstract: Along with the raising of the train speed, aerodynamic noise of the high-speed train is generated more and more significantly and their reduction has become one of the key factors to control noise of the high-speed train. Aerodynamic noise radiated from the high-speed train surface was analyzed numerically. The mathematical and physical models of the three dimensional flow field of the high-speed train were established and the external steady and unsteady flow fields of the high-speed train were calculated by using the standard "k-ε" turbulence model and large eddy simulation (LES) respectively. On the basis of the steady flow field, aerodynamic noise sources on the car body surface of the high-speed train are calculated by using the broadband noise source model. On the basis of the unsteady flow field, the time domain characteristics of fluctuating pressures on the car body surface are analyzed. The sound pressure level on the surface pressure demonstrating is calculated and the flow field of some critical parts is analyzed.

Abstract: Under summer climatic features of Daqing area in China, numerical simulation on the unsteady heat transfer characteristic of phase change roof was investigated, considering direct influence of solar radiation. The main influencing factor of latent heat in the phase change roof was analyzed in this paper. The results show that, latent heat in different phase change temperature has little effect on hourly distribution of average temperature and average heat flux of base upper surface. Choosing appropriate phase transition temperature is still the key to take efficient and reasonable adventage of phase change materials in the roof structures.

Abstract: When wrapping angle of cold strip covering surface of shape detecting roll dynamically changes, online radial pressure of the shape detecting roll is changed too, and it seriously affects online shape detecting precision of cold strip. The cold strip online dynamic wrapping angle compensation model is established, and successfully applied in 1250 mm 6-high cold mill, remarkable results is achieved. The error between calculated values and measured values of total tensions is within 3%.