Design and Dynamic Simulation Analysis of a Wheel–Track Composite Chassis Based on RecurDyn

The traditional chassis has the problems of low trafficability and poor stability under complex and changeable unstructured conditions. Thus, a wheel rail composite chassis is proposed. The chassis had a tracked travel mechanism at the front wheels and a wheeled travel mechanism at the rear wheels. This study presents the design, theoretical analysis and dynamic simulation analysis of the chassis. The maximum values of the passability of the wheel–track composite chassis that can be passed were calculated according to the relevant parameters. Furthermore, the chassis was modeled and simulated using RecurDyn to verify whether the values were reasonable. According to different values of the terrain, slope, vertical obstacle height and trench width, the change regularity of the track tension and driving torque of the chassis were obtained. The chassis is designed to improve the vehicle’s ability to operate under complex and diverse unstructured conditions.

Study on Film Cooling Performance of Round Hole Embedded in Different Shaped Craters and Trenches

Film cooling effectiveness can be improved significantly by embedding a round hole in trenches or craters. In this study, film cooling performances of a transverse trench, W-shaped trench and elliptic trench were compared and analyzed in detail. The CFD models for trench film cooling were established and validated via the experimental results. Inside the transverse trench, a pair of recirculating vortices is formed, which promotes the coolant spreading in a lateral direction. The decrease of trench width and increase of trench depth both improve the film cooling effectiveness of the transverse trench. For the W-shaped trench, the guide effect of the corner angle further improves the lateral spreading capability of coolant and generates higher cooling effectiveness than a transverse trench with the same depth and width. The flow characteristics of the elliptic trench are similar to that of the round hole, and the kidney vortex pair takes a dominant role in the flow fields downstream of the coolant exit. Accordingly, the elliptic trench generates the worst cooling performance in these shaped trenches. The increase of trench depth and decrease of trench width both result in an increase of the discharge coefficient for trench film cooling. For the W-shaped trench, the increase of the corner angle causes a decrease of the discharge coefficient. For the elliptic trench, the discharge coefficient increases with the decrease of the elliptic aspect ratio (major axis/minor axis).

Performance Enhancement in Multicore Fiber Using Trench Assisted Technique

Analysis of crosstalk in multicore fiber using trench assisted technique. To reduce the crosstalk between the cores in the fiber the coupled mode theory and coupled power theory are adopted for crosstalk estimation and considering different design parameters such as core pitch, bending radius and wavelength to optimize the crosstalk performance. The homogeneous fiber which works under single mode operation has been considered. The study of performance by varying the trench width is also analysed. Crosstalk variation in outer cores and center core of the fiber is studied. And the study of variation of crosstalk with 5 different core radius has been done. The numerical simulation results of crosstalk behavior over bending radius, wavelength and trench width is obtained.

Blue to yellow emission from (Ga,In)/GaN quantum wells grown on pixelated silicon substrate

It is shown that substrate pixelisation before epitaxial growth can significantly impact the emission color of semiconductor heterostructures. The wavelength emission from InxGa1−xN/GaN quantum wells can be shifted from blue to yellow simply by reducing the mesa size from 90 × 90 µm2 to 10 × 10 µm2 of the patterned silicon used as the substrate. This color shift is mainly attributed to an increase of the quantum well thickness when the mesa size decreases. The color is also affected, in a lesser extent, by the trench width between the mesas. Cathodoluminescence hyperspectral imaging is used to map the wavelength emission of the InxGa1−xN/GaN quantum wells. Whatever the mesa size is, the wavelength emission is red-shifted at the mesa edges due to a larger quantum well thickness and In composition.

Transmission and Reflection Characteristics of Perforated Submerged Single and Multiple Artificial Reef Units

Submerged breakwaters formed by natural rocks dissipate the incident wave energy. Continuous quarrying of rocks has resulted in its depletion, leading researchers to look for alternate materials for the formation of such barriers. Thus, the concept of artificial reef units has evolved which has been gaining importance owing to the flexibility in molding to any desired shapes and sizes, workability and also due to the fact that it creates a habitable environment to marine flora and fauna. From the hydrodynamic performance perspective, artificial reef units are proven to be more efficient in reducing wave transmission on the lee side (e.g., Southern Caribbean shore of Dominican Republic and Vaan Island, Tuticorin, India). A comprehensive experimental investigation to examine the effect of trench width on hydrodynamic characteristics of the submerged reef system was carried out. The trench width was varied by incorporating single, double, and multiple perforated submerged trapezoidal artificial reef units. The focus of the present study is mainly on the influence of the number of reef units, relative crest width, and relative trench width of the submerged reef system on its transmission and reflection characteristics. The relative trench width was found to be an influential factor on wave transmission past the structure, and the least wave transmission was achieved for the reef configuration with eight units. The details of the experimental investigation, results and discussion are reported in this paper.

High Resolution Heat Transfer Measurements of Cylindrical Holes Embedded in a Trench With Backward Injection

Recent studies have demonstrated that cylindrical hole with backward injection arrangement, of which the jets are injected reverse to the mainstream flow direction, outperforms its forward injection counterpart, of which the jets are injected along the flow direction, at high blowing ratio, since the jet starts to lift off typically for forward injection when blowing ratio is greater than 1.0. However, the backward injection configuration features a large separation and induces high heat transfer near the hole. Relative few studies have been conducted to mitigated the drawbacks of backward injection arrangements. The present study investigated several flat plate trenched hole arrangements with backward injection. Experiments were conducted in a low speed suction type wind tunnel. The trench width was varied from 2d to 4d for the backward arrangements with fixed trench depth of 0.75d. Besides, a simple backward and a trenched hole with forward injection, whose width is 2d and depth is 0.75d, were also studied as references. Transient thermal measurements were carried out for all the arrangements with IR camera. Detailed distributions of heat transfer coefficient were obtained. For each case, blowing ratio was varied from 0.25 to 4.0, while the density ratio was almost unity. Effects of injection angle, trench width and blowing ratio on the surface heat transfer distributions were obtained, and the results are presented and explained in this investigation.

Numerical Study on the Influence of Trench Width on Film Cooling Characteristics of Double-Wave Trench

Film cooling performance of the double-wave trench was numerically studied to improve the film cooling characteristics. Double-wave trench was formed by changing the leading edge and trailing edge of transverse trench into cosine wave. The film cooling characteristics of transverse trench and double-wave trench were numerically studied using Reynolds Averaged Navier Stokes (RANS) simulations with realizable k-ε turbulence model and enhanced wall treatment. The film cooling effectiveness and heat transfer coefficient of double-wave trench at different trench width (W = 0.8D, 1.4D, 2.1D) conditions are investigated, and the distribution of temperature field and flow field were analyzed. The results show that double-wave trench effectively improves the film cooling effectiveness and the uniformity of jet at the downstream wall of the trench. The span-wise averaged film cooling effectiveness of the double-wave trench model increases 20–63% comparing with that of the transverse trench at high blowing ratio. The anti-counter-rotating vortices which can press the film on near-wall are formed at the downstream wall of the double-wave trench. With the double-wave trench width decreasing, the film cooling effectiveness gradually reduces at the hole center-line region of the downstream trench. With the increase of the blowing ratio, the span-wise averaged heat transfer coefficient increases. The span-wise averaged heat transfer coefficient of the double-wave trench with 0.8D and 2.1D trench width is higher than that of the double-wave trench with 1.4D trench width at the high blowing ratio conditions.