A Smart Wing Rib Structure Suitable for Design for Additive Manufacturing (DfAM) Process

Additive manufacturing has been adopted widely across various industries for producing parts mainly due to their ability to create complex geometries, eliminate material wastage and enable faster production rate, among others. Additive manufacturing has also increased design solution space by enabling exploration of mechatronic solutions for mechanical structures. This includes the integration of smart devices into wing structures to achieve a datadriven predictive maintenance-based system. For this, there is still the need to continuously explore various ways of integrating sensory capability into a mechanical structure during the manufacturing processes to ensure improvement and reliability of aircraft components. The scope of this paper was to analyse different wing rib geometries and the influence of embedding sensory capability via design for additive manufacturing process. In this work, three wing rib geometries with cut-outs and for sensory placement were designed and analysed to estimate their equivalent stress and deformation when such sensory locations are introduced. The results confirm the idea that it is feasible to introduce holding cavities for structural performance monitoring sensors without compromising the structural design requirements. The results also show that deformation and stress are highly dependent on the rib thickness and the insertion of sensory locations

The Influence of Electro-Conductive Compression Knits Wearing Conditions on Heating Characteristics

Textile-based heaters have opened new opportunities for next-generation smart heating devices. This experiment presents electrically conductive textiles for heat generation in orthopaedic compression supports. The main goal was to investigate the influence of frequent washing and stretching on heat generation durability of constructed compression knitted structures. The silver coated polyamide yarns were used to knit a half-Milano rib structure containing elastomeric inlay-yarn. Dimensional stability of the knitted fabric and morphological changes of the silver coated electro-conductive yarns were investigated during every wash cycle. The results revealed that temperature becomes stable within two minutes for all investigated fabrics. The heat generation was found to be dependent on the stretching, mostly due to the changing surface area; and it should be considered during the development of heated compression knits. Washing negatively influences the heat-generating capacity on the fabric due to the surface damage caused by the mechanical and chemical interaction during washing. The higher number of silver-coated filaments in the electro-conductive yarn and the knitted structure, protecting the electro-conductive yarn from mechanical abrasion, may ensure higher durability of heating characteristics.

Influence of automobile sealing rib structure on sound insulation performance and optimization of section parameters

The door sealing strip plays an important role in the sound insulation of the car, and its sound insulation performance has a great influence on the sound quality and comfort of the vehicle. The sound insulation performance of the seal can be analyzed by Finite Element-Statistic Energy Analysismodel. There are great differences in the cross-section of the door sealing strip system at different positions, which leads to the difference of sound insulation. Therefore, it is very important to study the sound insulation performance of the sealing strip by studying the parameters of different sections. This paper explores the influence of the structure of automobile sealing rib on the sound insulation performance. Taking the sound power of the receiving end of the sealing strip as the index, the orthogonal optimization test is carried out for the simplified section shape of the door seal strip: the wall thickness of the sealing strip, the height of the sealing strip and the rib length. The optimal combination of a set of sealing strip sections is established, and the sound insulation performance of the sealing strip is improved.

Effect of Roughness Elements on the Evolution of Thermal Stratification in a Cryogenic Propellant Tank

The cryogenic propulsion era started with the use of liquid rockets. These rocket engines use propellants in liquid form with reasonably high density, allowing reduced tank size with a high mass ratio. Cryogenic engines are designed for liquid fuels that have to be held in liquid form at cryogenic temperature and gas at normal temperatures. Since propellants are stored at their boiling temperature or subcooled condition, minimal heat infiltration itself causes thermal stratification and self-pressurization. Due to stratification, the state of propellant inside the tank varies, and it is essential to keep the propellant properties in a predefined state for restarting the cryogenic engine after the coast phase. The propellant’s condition at the inlet of the propellant feed system or turbo pump must fall within a narrow range. If the inlet temperature is above the cavitation value, cavitation will likely to happen to result in the probable destruction of the flight vehicle. The present work aims to find an effective method to reduce the stratification phenomenon in a cryogenic storage tank. From previous studies, it is observed that the shape of the inner wall surface of the storage tank plays an essential role in the development of the stratified layer. A CFD model is established to predict the rate of self-pressurization in a liquid hydrogen container. The Volume of Fluid (VOF) method is used to predict the liquid–vapor interface movement, and the Lee phase change model is adopted for evaporation and condensation calculations. A detailed study has been conducted on a cylindrical storage tank with an iso grid and rib structure. The development of the stratified layer in the presence of iso grid and ribs are entirely different. The buoyancy-driven free convection flow over iso grid structure result in velocity and temperature profile that differs significantly from a smooth wall case. The thermal boundary layer was always more significant for iso grid type obstruction, and these obstructions induces streamline deflection and recirculation zones, which enhances heat transfer to bulk liquid. A larger self-pressurization rate is observed for tanks with an iso grid structure. The presence of ribs results in the reduction of upward buoyancy flow near the tank surface, whereas streamline deflection and recirculation zones were also perceptible. As the number of ribs increases, it nullifies the effect of the formation of recirculation zones. Finally, a maximum reduction of 32.89% in the self-pressurization rate is achieved with the incorporation of the rib structure in the tank wall.

Heat Transfer Measurements for Array Jet Impingement With Castellated Wall

Impingement cooling is one of the powerful cooling methods in high-temperature devices. For the gas turbine applications, impingement cooling is commonly applied in the transition piece of a combustor and in the leading edge, suction and pressure sides of a turbine blade/vane. In the suction side and pressure side, impingement cooling is applied as a form of an array jet. However, due to the small gap between the jet hole and target surface, the wall jet faces a crossflow inside of the gap. This crossflow has an adverse effect on the jets and deteriorates the heat/mass transfer performance. Therefore, several studies have been conducted to minimized the crossflow effect. The present study also investigated the effect of crossflow reduction in the gap by having a castellated hole plate. The heat/mass transfer was measured using the naphthalene sublimation method. Heat/mass transfer data are compared among three different cases. One is the baseline case which is simple array impinging jets. Others are the castellated cases with and without rib structures on the target wall. Jet-to-jet spacing (s/d) and jet-to-target spacing (z/d) are selected as geometrical variables. Also, the experiments were conducted for the Reynolds numbers (based on jet hole diameter) of 5,000, 15,000 and 30,000. The baseline case was named as B case, the castellated case without rib structure as C case and with rib structure as CR case. Both C and CR cases showed the crossflow reduction effect and resulted high and similar Nusselt number values.

Experimental study of turbulent flow and heat transfer behaviors over a micro-rib-dimple-structured surface

An experimental study was conducted to characterize the evolution of turbulent boundary layer flow over a micro-rib-dimple-structured surface. In addition to measuring the surface pressure distribution and detailed flow field inside the dimple cavity, the heat transfer performance over the rib-dimpled surface was investigated using transient liquid crystal thermography. The flow field measurements were correlated with the heat transfer measurements to elucidate the underlying physical mechanism of the improvement in thermal efficiency due to the micro-rib structure. It was found that, compared to the dimpled surface, the micro-rib structure induces a stronger downwash flow and acts as a tabulator to enhance the turbulent mixing of the downstream flow, which significantly restricts the flow separation and the recirculating flow inside the dimple cavity. The dominant flows inside the dimple cavity are the downwash and successive upwash flows, which significantly enhance the turbulent mixing and consequently, improve the heat transfer performance over the rib-dimpled surface. The measurements of the pressure loss and heat transfer performance indicated that the rib-dimpled surface has an overall thermal efficiency approximately 12%−16% higher than that of the dimpled surface owing to the micro-rib structure.

Natural convection in an enclosure with fins in the presence of non-uniform temperature pro-file at vertical wall

The development of energy instrumentation, electronic industry and energy in general is inextrica-bly linked with the intensification of heat and mass transfer occurring in the base units and aggre-gates of energy systems. One of the approaches to solving this problem is to create an extended heat transfer surface by introducing a rib structure or porous inserts. This work is devoted to math-ematical modeling of natural convection in an enclosure in the presence of a rib structure and non-uniform temperature profile on one of the vertical walls. The governing partial differential equa-tions written using dimensionless non-primitive variables “stream function – vorticity – tempera-ture” based on the Boussinesq approximation, in combination with initial and boundary conditions, have been worked out on the basis of the finite difference method. The developed computational model was varified using the mesh independence test and benchmark problems solved by other au-thors. Numerical investigations of unsteady natural convection of viscous fluid in a cavity with a variable temperature on the left wall under an influence of a rib structure have been carried out for the following values of governing parameters: Pr = 0.71, 103 < Ra < 106, and the number of ribs varied from one to three. Distributions of streamlines and isotherms, as well as the dependences of the average Nusselt number and average cavity temperature, were obtained for a steady mode. As a result of the analysis, it has been found that the addition of solid ribs allows to enhance the heat transfer for low Rayleigh numbers, while for Ra  105 one can find an attenuation of convective heat transfer. A growth of the fins heat conductivity characterizes the heat transfer enhancement.

Discussion of 800m Composite Bridge with CFST Flying Swallow Arch and Self-anchored Suspension Cable

In view of the demand of 800 meters Super Long Span CFST arch bridge, the composite bridge of CFST flying swallow arch and self-anchored suspension cable is proposed. The thrust of flying-bird CFST arch bridge and the tension of self-anchored suspension bridge are balanced, forming a self-balanced structure system. The arch rib structure is mainly stressed, supplemented by the self-anchored suspension system, which works together and has complementary advantages. Using the single leaf hyperboloid variable section steel tube four limb space truss arch rib structure, the self-weight of the mid span arch rib section structure is reduced, the risk of construction and hoisting of the mid span section is reduced, the section size at the arch foot is increased, the mass center and stiffness center of the arch bridge structure are effectively reduced, and the stability of the super long span concrete-filled steel tube arch bridge is increased. Combined with the actual project, the parameters are designed, the Midas finite element model is established, the internal force analysis and calculation, modal analysis and buckling analysis are carried out, and the superiority of the structural technical measures is verified.