Study Of Design Parameters Research Articles

Fluid-thermo-structural response of actively cooled scramjet combustor in hypersonic accelerating-cruise flight

This paper presents a three-dimensional transient fluid-thermo-structural study of an actively cooled sandwich panel under hypersonic accelerating-cruise flight conditions. The thermo-structural loads are estimated using a high-speed gas-dynamic flow model combined with Eckert's reference temperature method. The thermal safeguard capacity with endothermic fuel-based active cooling shows design optimization scope compared to the passive system. A passive system has to survive excessively high temperatures with a less severe thermal gradient over the panel thickness and a high heat leakage into the structural interior or back wall. The actively cooled system with fuel develops significant panel bending due to a through-thickness thermal gradient in the cooling channels. For a Mach 7 flight, an actively cooled system reduces the bending deformation by 90% and improves the thermal safeguard capacity by 70% compared to a passive approach. Active cooling can effectively control the excessive thermo-structural deformation and fuel heating below its cracking temperature to improve combustion. Our parametric design study indicates the influence of fuel as a coolant for increasing combustion efficiency and the associated complexity and trade-off in the heat transfer and thermo-structural deformation behavior. This transient response under hypersonic accelerating-cruise flight conditions requires a careful review of the scramjet engine thermo-structural design philosophy. The design approach has applications in bodies encountering highly transient thermo-structural loads with differently purposed fuels/coolants.

Parametric study for hydraulic design of air-bubble injections to control scour around circular bridge piers

ABSTRACT Several countermeasure techniques have been presented to control bridge scour-induced failure. Air-bubble injection, a new method compatible with the environment, was introduced to combat destructive vortices that cause bridge piers to be scoured. Extensive experiments were conducted to determine the appropriate air-bubble injections for the least scours at a bridge pier. Two different clear-water flow intensities with air-bubble injections were assessed in different radial positions around and also on the upstream half of the bridge pier. The vertical position of air injections and air discharge were determined previously to be optimal. The long-term experiments revealed that the well-designed air-bubble injections reduced the local scour around the bridge pier. It was found that the complete air-bubble injection around the bridge pier is the best configuration and able to reduce the scour depth about 44% over the case with no air injection (non-protected pier). Moreover, the appropriate arrangement of bubble injections to lessen the scour depth is the nearest radial position of the injection to the bridge pier and with increasing the radial distance of injections to the pier, the bubble plumes move downstream by the main flow. The results indicate that bubble plumes would be effective in both flow intensity, u*/u*c = 0.7 and 0.9, as examined in the present study.

Parametric design and IR signature study of exhaust plume from elliptical-shaped exhaust nozzles of a low flying UAV using CFD approach

This paper describes the design, parametric study, and IR signature analysis of plume of a slit-shaped exhaust nozzle. Circular-shaped exhaust nozzles are generally used to get the essential thrust necessary for an aircraft flight. However, the Infrared (IR) signature of the exhaust plume emanating from these nozzles is very high, and the IR missile can easily lock and hit the aircraft. In this paper, the compressible flow CFD model using a realizable k-ε turbulence model is used to study the flow characteristics of the exhaust nozzle with different aspect ratios. The exit cross-section of the nozzle is kept elliptical up to a maximum aspect ratio of 10. IR signature for each nozzle shaped is calculated using a set of input parameters in Mid-wave IR and Long-wave IR spectral bands. The IR signature of exhaust plume in Long-wave IR spectral band is not significant due to high transmittance of species in the exhaust plume mixture. However, for this particular case of low flying UAV, a considerable reduction in the IR signature is recorded for the high aspect ratio nozzle in MWIR spectral band.

An Absorbing Improvement for Space Infection Decompression: A Novel Drainage Device.

IntroductionInfection of the facial spaces and the associated exudate can often necessitate surgical intervention. Whilst traditional decompression methodologies have reduced the mortality rate from complications such as Ludwig’s Angina, there has been relatively little innovation in the procedure to minimize treatment times and patient distress. Negative pressure wound therapy, which can yield improvements to treatment time, wound healing and patient experience, has gained traction in abscess treatments in other parts of the body but seen limited adoption in maxillofacial surgeries.MethodsA focused literature review explores the existing treatment methodologies for infected facial space decompression and identifies obstacles to implementing negative pressure wound therapy in maxillofacial surgeries. A novel drainage tool, which features a sleeved sponge over a perforated drainage tube, is proposed. Virtual prototyping and structural analyses of the novel drainage device including a parametric design study are presented.ResultsThe parametric study validates the proposed tool’s biocompatibility in terms of overall flexural and axial stiffness between the tool and complex structures in the head and neck. Ultimately, this work presents a necessary first step in the development of specialized drainage tools to promote the adoption of negative pressure wound therapy for infections of facial spaces.

Brillouin-zone characterization of piezoelectric material intrinsic energy-harvesting availability

Vibration energy harvesting is an emerging technology that enables electric power generation using piezoelectric devices. The prevailing approach for characterization of the energy-harvesting capacity in these devices is to consider a finite structure operating under forced vibration conditions. Here, we present an alternative framework whereby the intrinsic energy-harvesting characteristics are formally quantified independent of the forcing and the structure size. In doing so, we consider the notion of a piezoelectric material rather than a finite piezoelectric structure. As an example, we consider a suspended piezoelectric phononic crystal to which we apply Bloch’s theorem and formally quantify the energy-harvesting characteristics within the span of the unit cell’s Brillouin zone (BZ). In the absence of shunted piezoelectric circuits, the wavenumber-dependent dissipation of the phononic crystal is calculated and shown to increase, as expected, with the level of prescribed damping. With the inclusion of the piezoelectric elements, the wavenumber-dependent dissipation rises by an amount proportional to the energy available for harvest which upon integration over the BZ and summing over all branches yields a quantity representative of the net available energy for harvesting. We investigate both monoatomic and diatomic phononic crystals and piezoelectric elements with and without an inductor. The paper concludes with a parametric design study yielding optimal piezoelectric element properties in terms of the proposed intrinsic energy-harvesting availability measure.

Design subspace learning: Structural design space exploration using performance-conditioned generative modeling

Designers increasingly rely on parametric design studies to explore and improve structural concepts based on quantifiable metrics, generally either by generating design variations manually or using optimization methods. Unfortunately, both of these approaches have important shortcomings: effectively searching a large design space manually is infeasible, and design optimization overlooks qualitative aspects important in architectural and structural design. There is a need for methods that take advantage of computing intelligence to augment a designer's creativity while guiding—not forcing—their search for better-performing solutions. This research addresses this need by integrating conditional variational autoencoders in a performance-driven design exploration framework. First, a sampling algorithm generates a dataset of meaningful design options from an unwieldy design space. Second, a performance-conditioned variational autoencoder with a low-dimensional latent space is trained using the collected data. This latent space is intuitive to explore by designers even as it offers a diversity of high-performing design options.

The effect of control rods on the reactivity and flux distribution of BWR 4 bundle using MCNPX Code

This paper has three main objectives related to the neutronic and burnup analysis of the BWR (Boiling Water Reactor) Four-Lattice. The first objective is to provide partial validation of the MCNPX code for this lattice by comparing its results with Scale-5.1 results. Validation of the MCNPX to calculate effective multiplication factor and reactivity rod worth for the F-Lattice is provided. This is carried out in case of instantly removing the control blade and replacing it with a graphite moderator. Moreover, spatial neutron flux distributions using F-mesh card over the bundle and the control blade are investigated at inserting and withdrawing the B4C. The second objective is to perform parametric design studies of the F-Lattice. Areas of particular interest are the effect of increased or decreased blade width on the neutron flux throughout the bundle. It is found that the presence of carbon in the control blade at withdrawing the B4C makes the reactor supercritical, (K-eff = 1.22206). On the other hand, the use of B4C blade presents (K-eff = 0.93521). Consequently, the reactivity of 10% B4C thinner case is higher that of 10% B4C thicker. The simulation also showed that the B4C blade had an effective role in decreasing the thermal flux at the periphery of the bundle. This is contrast to the effect of carbon that moderates fast to thermal neutrons. The third part of this work aims at studying the burnup calculations using MCNPX code for 30 days burn with 1 day time step then for 20 months burn with 2 week time steps for the lattice. At the end of the work, it is very important to determine the most proper bundle model that achieves a prolonged fuel burn and flatting thermal flux distribution. For reaching this goal, three cases (B4C, 10% thinner of B4C and 10% thicker) are simulated by MCNPX code till 70 GWd/ton. It is found that the B4C and 10% thicker are the appropriate models that can satisfy the safety considerations of the Compact Modular Boiling Water Reactor.

Buckling of Rectangular Composite Pipes under Torsion

The numerical buckling load of rectangular composite pipes under torsional load was derived by using the energy method. The authors found no available simple design method or chart for the buckling loads of rectangular composite pipes, which are often used airplanes, spacecraft, and other lightweight structures, through their involvement in a Mars exploration airplane project. Thus, numerical results were obtained for length-to-width ratios (l/b) from 1 to 20, width-to-height ratios (h/b) from 1 to 6, and [0/90] layer ratios (r) from 0 to 1, which means [(0/90)r,(±45)1-r]s. The layups were assumed to be symmetric, and tension-bending, torsion-bending, and tension-shear coupling stiffnesses were ignored. To establish a simple design method, a closed-form polynomial equation for the buckling load factor was derived by minimizing the weighted residuals of the safe and non-safe side errors, which were obtained by comparing the derived numerical results with the polynomial equations. As a result, the errors of the polynomial equation for the buckling load factor were 4.95% for the non-safe side and 12.4% for the safe side. The errors are sufficiently good for preliminary design use and for parametric design studies and optimization.

Conceptual Design of Composite Bridge Sandwich Structure

Fiber-reinforced polymer (FRP) composite bridges are usually constructed for rapid installation. The durability of the bridge is increased by stiffness, strength to weight ratio, and corrosion resistance. The main factors on which the design of the composite sandwiched bridge considerably depends are ply layers, material system, alignment of ply angles, and thickness of the core. In this work, a parametric design study for a bridge using finite element analysis (FEA) is presented. Two types of composite materials—carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP)—were used as the sandwich structure’s skin, and three different types of woods were used as a core. Different design configurations were acquired based on material and instability constraints by using Euro-codes. Failure criterion of Tsai-Hill, Tsai-Wu, MS, equivalent stress, and maximum shear stress were implemented to analyze the overall failure of the bridge deck under Ultimate Limit State (ULS) conditions. The total deformation was examined under Serviceability Limit State (SLS) conditions, and the results were compared and verified by the previous study. The core was also examined using the core-factor and increasing the thickness of the core through parametric modeling.

Parametric slat design study for thick-base airfoils at high Reynolds numbers

Abstract. Standard passive aerodynamic flow control devices such as vortex generators and gurney flaps have a working principle that is well understood. They increase the stall angle and the lift below stall and are mainly applied at the inboard part of wind turbine blades. However, the potential of applying a rigidly fixed leading-edge slat element at inboard blade stations is less well understood but has received some attention in the past decade. This solution may offer advantages not only under steady conditions but also under unsteady inflow conditions such as yaw. This article aims at further clarifying what an optimal two-element configuration with a thick main element would look like and what kind of performance characteristics can be expected from a purely aerodynamic point of view. To accomplish this an aerodynamic shape optimization procedure is used to derive optimal profile designs for different optimization boundary conditions including the optimization of both the slat and the main element. The performance of the optimized designs shows several positive characteristics compared to single-element airfoils, such as a high stall angle, high lift below stall, low roughness sensitivity, and higher aerodynamic efficiency. Furthermore, the results highlight the benefits of an integral design procedure, where both slat and main element are optimized, over an auxiliary one. Nevertheless, the designs also have two caveats, namely a steep drop in lift post-stall and high positive pitching moments.

A numerical study on particle tracking and heat transfer enhancement in a solar cavity receiver

The thermochemical dissociation of natural gas into hydrogen and carbon involves the presence of solid phase carbon particles. In addition to the produced carbon, carbon particles can be seeded to the process as a catalyst which act both as a heat transfer enhancing medium and nucleation site for the dissociation reaction. However, presence of discrete phase particles imposes various challenges such as deposition on solar reactor walls and windows, and clogging of the exhaust. Meticulous reactor-receiver design optimization is therefore required and is presented in this study. The Discrete Phase Model (DPM) was implemented in a numerical CFD model to track injected carbon particles in a Lagrangian framework. Validation of the model was done with respect to available experimental data and showed similar deposition phenomena on the reactor window. A parametric design study was performed taking into account flow rates, particle size, particle loading and receiver geometry. Use of a finer particle size distribution demonstrated the ability of the flow to entrain more particles to the exhaust and reduce deposition on the bottom wall of the cavity. Three design iterations on an existing 1 kW solar cavity receiver were proposed, depicting an increase of at least 6.5% on the outlet gas temperature and 4% on the overall average gas temperature within the receiver. Results of this study highlighted the importance of flow configuration, flow parameters and particle size on the deposition and heat transfer inside solar cavity receivers. Outcome of this study can serve as a reference for solar reactor design involving presence of particulate media.

Parametric study for shear design of cold-formed channels with elongated web openings

Cold-formed steel members are commonly perforated with elongated web openings in practice to allow more access for the building service systems. The presence of such extended web holes in the members, when subjected to high shear forces, influences the shear buckling characteristics, the shear failure modes and generally leads to a reduction of shear capacity as well. In order to provide a better insight into the shear behaviour of cold-formed members with elongated web cut-outs, this paper presents a numerical study using finite element method (FEM) models employing ABAQUS/Standard to investigate the elastic shear buckling and post-buckling behaviour of cold-formed members in the form of thin channel sections. A full non-linear FEM model is developed and calibrated against previous shear tests with elongated web holes carried out using a dual actuator test rig. Based on the successful calibration against the tests, a parametric investigation is conducted to extend the resulting database. Further, a new proposal for the Direct Strength Method (DSM) of design of perforated channels in shear with both non-elongated and elongated web holes is further validated by using the results from the parametric study. A comparison between the empirical approach (“qs” method) and the new DSM of design derived from the Vierendeel mechanism approach is also provided to enhance the applicability of the new proposal to different cases of perforated channel members in shear with a wider range of sectional dimension and thicknesses.

Analysis and verification of the degree of bending isotropy of thin laminated composites manufactured using non-crimp fabric

Laminated composites generally provide anisotropic stiffness properties depending on their stacking sequences. These anisotropic properties are not desired for certain applications that are subjected to multi-directional loadings requiring optimal stiffness properties in all directions. As a result, this paper aims to present a formulation for assessing the degree of isotropy of thin laminated composites. The starting laminate configuration chosen is a quasi-isotropic laminate in which extensional isotropy is inherently satisfied. As for the degree of bending isotropy, it can be quantified from a generalized eigenvalue problem of the bending stiffness tensor. A new lay-up strategy is proposed for thin-ply non-crimp fabric (NCF), and a parametric design study was conducted on quasi-isotropic NCF to maximize the degree of bending isotropy. Using mid-plane symmetric and non-symmetric laminate configurations, the maximum degree of bending isotropy is achieved for non-symmetric ones. A fully isotropic laminate (FIL) can be obtained when both in-plane and bending stiffness tensors are equivalent to the isotropic stiffness counterpart with null coupling stiffness. Starting with a quasi-isotropic 3-ply NCF as the building block, a non-symmetric fully isotropic laminate with 18 plies was obtained. Two laminate designs composed of NCFs with different degrees of bending isotropy were manufactured for experimental verification using three-point bending testing, and the results validate a direct relation between the degree of bending isotropy and the flexural stiffnesses at multiple directions.

Identification of efficient geometries for variable pitot inlets for supersonic transport

PurposeThis paper aims to reveal the influence of selected geometric parameters on the aerodynamic performance of circular variable aero engine inlets in transonic and supersonic civil aviation.Design/methodology/approachThe trade-off in inlet design and aerodynamic evaluation parameters is presented. The approach to investigate the dependencies between the aerodynamic and geometric parameters at different flight conditions by means of a parametric design study is introduced.FindingsThe dependencies of inlet drag and efficiency from geometric parameters at flight speeds of Mach 0.95 up to Mach 1.6 are identified. Although entailing additional weight, the inlet length represents the parameter with the highest potential for drag reduction by up to 50% in the selected design space. Ideal geometries for variable pitot inlets are determined. After considering weight, their potential range benefit nearly disappears for subsonic applications, but remains above 20% for supersonic flight at Mach 1.6.Originality/valueHence, the technology of circular variable pitot inlets for supersonic transport aircraft could be a way to achieve the ambitious ecological, safety and economic goals for future civil aviation.

Parametric design study of a substrate material for a DEMO sacrificial limiter

Abstract Towards the realization of nuclear fusion, a future reactor must provide efficient and safe power exhaust through both the divertor and FW. Recent studies suggest that the greatest engineering challenges of plasma-facing components (PFCs) may arise from the occurrence of plasma transients, when extreme heat fluxes are expected. In severe cases, extensive surface vaporization, melting and re-solidification may lead to excessive degradation of conventional PFCs. An eventual failure would compromise the reactor safety as well as its prompt return to normal operation. A sacrificial limiter provided with a micro-engineered substrate material is being investigated for DEMO to cope with the harsh conditions occurring during unmitigated plasma disruptions. Among the possible solutions, innovative materials such as tungsten (W) based lattice structures can be tailored to meet functional requirements and prevent severe failures. As a further step in this direction, an equivalent solid model, originally developed and validated for open-cell Al foams, was transferred to W foams and the scaling law of its thermo-physical properties evaluated as a function of the most influential parameters. In the present work, a design optimization tool for the thermal behavior of the substrate material is presented. The latter is modeled as a homogeneous material having equivalent properties. A parametric design study was carried out to assess their impact on the global behavior of the PFC. Independent combinations of equivalent thermal conductivity and density have been applied to the substrate material by scaling the corresponding properties of bulk W. For each design point, results were tabulated and compared with user-defined operating requirements. Afterwards, a post-processing routine was implemented for effective visualization of the space of solutions. Ultimately, tailored lattice structures potentially able to fulfill the operating requirements are proposed. An existing solid model for open-cell W foams was employed to design the features of such material based on the results of the parametric study.

Corrosion Behavior Studies and Parameter Optimization of Dissimilar Alloys Joined by Electron Beam Welding

A number of special alloys are used in harsh environments with extreme high temperatures due to their superior properties like good oxidation and creep resistance. Over the past few years, joining of dissimilar alloys using electron beam welding (EBW) has been of prime importance owing to its superior advantages. The related work primarily involves joining dissimilar alloys using special features like controlling location and beam size and promises less heat affected zone. The current research is focused on investigating the parameters of EBW on corrosion behavior of nickel-based super alloy and stainless steel. In order to optimize the number of experiments to be performed, Taguchi method is used. The weld joints are prepared as per the parametric design and potentiodynamic polarization studies have been carried out on the weldments in 5% NaCl environment in order to assess the corrosion behavior of welded materials.

Parametric facade approach for an office building to reduce the irradiance level in Jakarta

Energy used in multi-storey office building is mostly for air conditioning, and it is acknowledged that the energy could be minimized by reducing the cooling load. In general, the cooling loads are from internal and external heat. The external heat plays significantly in determining the cooling load; therefore, it is necessary to reduce the amount of solar radiation received by the external surface of the building. The objective of the paper is to investigate the reduction of solar radiation received by the surface of the multi-storey office building by applying parametric design study and to add a building envelope as the secondary skin as well as the architectural element. There are two steps of analysis in the methodology, (1) to conduct solar radiation analysis, and (2) to conduct building facade analysis. In the process, four alternatives form were simulated to obtain the most optimum shape in relation to the incident solar radiation reduction. The final parametric study results of the solar radiation and building facade analysis showed that the reduction of the irradiance is around 25% with the additional facades.

A parametric fin structure design study for cooling aerospace electro-mechanical actuators with high-speed axial fans

Despite their advantages compared to hydraulic actuators, electric actuators are prone to overheating due to their high heat dissipation. So, developing reliable cooling systems for electric actuators is a crucial task, especially for aerospace applications which require the fulfillment of high safety requirements. In this paper, an air-cooling system utilizing wing bay air is investigated. An axial fan sucks air to flow through a shrouded-fin surface attached to the motor housing. A CFD model is developed to study the heat transfer and air flow processes over the finned surface. The relation between the fan pressure jump with the volumetric flow rate of a high speed SUNON fan at different rotational speeds and ambient pressures is measured in a fan loop and incorporated in the model. To validate the CFD results, a test rig consisting of a finned surface brazed on a heated aluminum cylindrical block and attached to a fan is built. The predicted and measured temperatures at different locations in the aluminum block show good agreement when the numerical simulation is performed using the k-ω-SST turbulence model. The average discrepancy of the predicted and measured steady state temperature differences (T-T∞) reduces from 1.6 °C for the k-e Realizable model to 0.31 °C for the k-ω SST model. Numerical simulation is performed to predict the effect of fin shape, fin number and fin thickness on the cooling performance of the fin structure. The results show that the straight plate fin configuration outperforms the offset-strip and corrugated fin. Also, it is found that there is an optimum value for the fin number, and this optimum fin number changes with the fan rotational speed and ambient pressure. Reducing the solidity of the fin structure by reducing the fin thickness results in improving the thermal performance when the fan operates at a low ambient pressure (0.2 atm). By comparing all data, it is found that the straight fin structure with 110 fins and fin thickness 0.2 mm is the optimum one. For fan speed of 12,000 rpm, this structure can restrict the thermal resistance between 0.17 °C/W at 0.2 atm and 0.047 °C/W at 1.0 atm.

Modelling and dynamic analysis of an anti-stall tool in a drilling system including spatial friction

This paper investigates the effects of a down-hole anti-stall tool (AST) in deviated wells on the drilling performance of a rotary drilling system. Deviated wells typically induce frictional contact between the drill-string and the borehole, which affects the drill-string dynamics. In order to study the influence of such frictional effects on the effectiveness of the AST in improving the rate-of-penetration and drilling efficiency, a model-based approach is proposed. A dynamic model with coupled axial and torsional dynamics of a drilling system including the down-hole tool in an inclined well is constructed. Furthermore, the frictional contact between the drill-string and the borehole is modelled by a set-valued spatial Coulomb friction law affecting both the axial and torsional dynamics. These dynamics are described by state-dependent delay differential inclusions. Numerical analysis of this model shows that the rate-of-penetration and drilling efficiency increases by inclusion of the AST, both in the case with and without spatial Coulomb friction. Furthermore, a parametric design study of the AST in different inclined drilling scenarios is performed. This study reveals a design for the AST, which gives optimal drilling efficiency, robustly over a broad range of inclined drilling scenarios.

Analytical modeling and analysis of rhombus-type amplifier based on beam flexures

In order to accurately reveal the kinematic characteristics, the nonlinearities of load-equilibrium equations associated with the deflection of the flexible elements cannot be neglected, especially for the distributed-compliance compliant mechanisms. The object of this paper is to present a nonlinear analytical model of rhombus-type amplifier based on the beam flexures and to evaluate the effect of forces so as to offer helpful for initial parametric design studies. Based on the beam constraint model (BCM), the nonlinear analytical models of the one-stage and two-stage rhombus-type amplifiers are established respectively with some permissible approximations. Then, the input stiffness and off-axis stiffness models are formulated respectively, and the stiffness characteristic analysis is also carried out. Additionally, finite element analysis (FEA) is conducted to evaluate responses of the model with various parameters under the action of different forces. Finally, experimental studies of the performances are carried out, and the experimental results are compared with the theoretical models and FEA results. The nonlinear behaviors in the displacement, amplification ratio and input stiffness are revealed accurately, and the reason why the amplification ratio of the two-stage amplifier is different from the expected value is explained.