Opening Ratio Research Articles

Effect of the J-Shaped Wind Turbine Airfoil Opening Ratio and Thickness on the Performance of Symmetrical Airfoils

Abstract In this work, the effect of the inner opening ratio on the J-shaped airfoils aerodynamic performance was studied and documented for symmetrical airfoils. Three different airfoil thicknesses were investigated: small (NACA0008), medium (NACA0015), and large (NACA0024). For each airfoil thickness, effects of three inner opening ratios were analyzed: one-third, one-half, and two-thirds. The performance of each opening ratio was compared with the performance of the solid airfoil “zero opening ratio” for different angles of attack between 5 deg and 20 deg. All designs were simulated using the computational fluid dynamics (CFD) technology against experimental results for solid NACA4412 airfoil in the University of Wisconsin-Milwaukee (UWM) wind tunnel facility and other published experimental data. It was found that large eddy simulation yields accurate solutions with a smaller number of mesh cells compared to the k–ω turbulence model but with much longer computational time. The lift-to-drag ratio for all studied airfoils has a maximum value for solid airfoils compared to those equipped with openings. For airfoils equipped with 00.00% opening ratio “solid,” NACA0015 airfoil has the maximum lift-to-drag ratio. Furthermore, it was found that NACA0008 equipped with a 33.33% opening ratio has the best performance of all studied J-shaped airfoils.

Influence of artificial roughness parametric variation on thermal performance of solar thermal collector: An experimental study, response surface analysis and ANN modelling

The influence of the attack angle (αa) of the perforated baffles on thermohydraulic performance ηp of a solar thermal collector (STC) has been investigated experimentally. The experimentations have been performed to obtain the Nusselt number (Nurs) and friction factor (frs) by varying Reynolds number (Re) from 5000 to 17,000 and αa from 35° to 65°. The other geometrical parameters of angled perforated baffles are fixed in accordance with previous studies. The relative baffle height HB/HD , relative baffle pitch PB/HB , relative hole position OB/HB and open area ratio β0 are fixed at 0.50, 10, 0.266 and 12% respectively. The STC with roughened angled perforated baffles improves the Nurs and frs by 3.82 and 7.14 times respectively as compared to STC without baffles wall. The angled perforated baffles at αa of 55° provides highest thermo-hydraulic performance at Re of 9000. A thermo-hydraulic performance of 1.94 is obtained for the array of designed parameters. The statistical correlations are established for the Nurs and frs by using experimental data. The correlations obtained for the Nurs and frs predict the experimental results within a variation of ±9.7% and ±5.0% respectively. Central Composite Design (CCD) of thermo-hydraulic performance parameters is carried for the surface response analysis. Modelling of thermal parameters using CCD and Artificial Neural Network (ANN) is done which predict them with good accuracy. The previously studies on STC roughened with various types of roughness show appreciable heat transfer enhancement but very few studies have utilized angled perforated baffles. As per author knowledge, a comprehensive study on the performance analysis of STC roughened with angled perforated baffles using different techniques is not available. The study become novel because in addition to the experimental examination of STC performance, correlations for Nurs and frs from experimental data are developed and modelling of thermal parameters using CCD and Artificial Neural Network (ANN) is also performed.

Test on axial compression performance of perforated welded H-shaped steel stub column

To determine the mechanical properties of perforated welded H-shaped steel stub columns subjected to the axial compression, 139 specimens including contrast group were tested under the axial compression. The ultimate bearing capacity and failure mode of members were studied by setting experimental variables, including the thickness of the web, flange thickness, opening diameter, and distance between column end and the web opening closest to the column end. The specimens presented several types of local failure modes. The load–displacement curve of the perforated specimens can be divided into three stages. For the specimens with dense web openings, the corresponding bearing capacity reduction coefficients were more obvious with an increase in the opening ratio. In addition, the rate of stiffness degradation was positively correlated with the opening ratio. The depth-thickness ratio of the web plate had a greater effect on the ductility of the specimen than that of the other parameters. By increasing the flange thickness, the stress concentration near the web opening was effectively reduced. The conclusions drawn from the parameter analysis were verified using finite element analysis. The calculation formula for the bearing capacity of performance of perforated welded H-shaped steel stub column was established and verified based on the test and finite element simulation results.

Effect of opening geometries on fire development in a ro-ro space

ABSTRACT A series of model scale experiments were conducted to study the fire development in a ro-ro deck with various opening geometries. The experiments were performed in a 1/8 reduced scale model with a heptane pool fire as fire source. Experimental results show that both the ventilation factor and the opening position affect the fire development. The critical opening ratio for the fire to self-extinguish is 4%, with the opening locating at the bottom of the side walls while no self-extinction is found for other tests. A higher opening position and a larger opening height provide better flow exchange between the deck and the ambient, but this effect is only obvious for 4% opening. Numerical study shows that Fire Dynamic Simulator used with default simple settings underestimates the fire development and yields an early extinction when fire self-extinction occurs. For freely developed fire with large openings, FDS gives more close results to experiments.

Research on the stability enhancement mechanism of multi-parameter interaction of casing treatment in an axial compressor rotor

The research on geometric parameters of casing treatment (CT) has always been a hot topic, yet the multi-parameter interaction is rarely studied. In order to gain better knowledge of the interaction mechanism of geometric parameters of CT, the experimental and numerical study based on the response surface method has been carried out in an axial compressor rotor. First of all, the statistical analysis based on the database of experimental and numerical results is presented to summarize the influence law of varied parameters on the stability enhancement. It was found that axial overlap, open area ratio, and their interaction had the most significant influence on the stability enhancement of CT. Subsequently, the interaction between axial overlap and open area ratio was analyzed by visualization flow field in details, which provided a deeper insight into stability enhancement mechanism of CT. It indicated that the mass flow and momentum dominated by injection and the suction effect played a key role for extending stability. With smaller open area ratio, it was difficult for the slots to manipulate and control the tip leakage flow or secondary tip leakage flow, resulting in the weak effect of CT on compressor performance. Finally, the underlying flow physics in the tip region and dominant region of CT has also been discussed to penetrate the essential reason of multi-parameter interaction.

Corrigendum to: The effect of openings ratio and wall thickness on energy performance in educational buildings

Corrigendum to: The effect of openings ratio and wall thickness on energy performance in educational buildings

Load Capacity of Perforated Reinforced Concrete Sewer Pipes

In cities, reinforced concrete pipes are often employed to construct storm sewer systems. Due to impervious base layers, stormwater runoff dominates rather than rainwater infiltration, leading to problems in aquatic ecosystems (e.g., degradation in urban watersheds, flood attenuation, and water quality). A thermoplastic perforated pipe can provide drainage channels in applications of solid waste landfills, mining heap leach pads, or irrigation systems. Inspired by these applications, perforation can be implemented in a reinforced concrete sewer to alter the moisture conditions in the ground under impervious base layers. Three-edge bearing tests and four-point flexural tests are conducted to investigate the structural integrity of perforated sewer pipes. A numerical model is also calibrated for use to optimize the layout design of drainage holes. It is found that perforation can result in strength degradation in concrete pipe, but the reduction in strength is not significant. A correlation between the ultimate load and opening ratio is established for the two testing conditions. The allowable opening ratio is determined as 0.2%, below which a perforated sewer can fulfill the requirements for both drainage and load resistance.

Multi-electron–ion coincidence spectrometer with a high-efficiency microchannel plate detector

A microchannel plate detector with a large open area ratio (nominally 90%) has been installed in a magnetic bottle electron spectrometer in order to improve the coincidence efficiency in multi-electron−ion coincidence measurements. The overall detection efficiency of the magnetic bottle spectrometer is determined to be ~70% for electrons with kinetic energies of up to at least 530 eV and ~85% for XeZ+ (Z > 3) ions. The usefulness of the improved detection efficiency in multi-electron−ion coincidence spectroscopy is demonstrated by a six-fold coincidence measurement about the quadruple Auger decay of the Xe 3d5/2 core-hole state.

Investigating the Aeroacoustic Properties of Porous Fabrics

The aeroacoustic properties of porous fabrics are investigated experimentally with the goal of finding a fabric that serves as an improved interface between wind tunnel flow and quiescent conditions. A total number of eight porous fabrics were investigated, namely, four glass fiber fabrics, two plain-weave Kevlar fabrics, and two modified plain Kevlar fabrics with their pores irregularly clogged. Two custom-made rigs were used to quantify the transmission loss (TL) and self-noise of all fabrics. The pores were found to serve as a low-resistance gateway for sound to pass through, hence enabling a low TL. The TL was found to increase with decreasing open area ratio (OAR), whereas other fabric properties had a minor impact on TL. The thread density was found to be a primary factor in determining the frequency range of porous fabrics’ self-noise, with the OAR potentially playing a secondary role in the self-noise levels. Fabrics with irregular pore distribution showed a more broadband self-noise signature associated with lower frequencies compared to fabrics with periodic pore patterns. Overall, fabrics with an irregular pore distribution or fabrics with increased thread density were identified as two potential ways to obtain superior aeroacoustic behavior compared to commonly used Kevlar fabrics.

Shear performance of SupaCee sections with openings: Numerical studies

Cold-Formed Steel (CFS) sections provide many design and construction sophistications including lightweight and high strength-to-weight ratio. The SupaCee section was introduced to CFS industry due to its cost effectiveness, enhanced strength, better structural performance and high stiffness. Introduction of SupaCee sections lead to investigations of web crippling, flexural and shear behaviour of the sections. However, structural behaviour of SupaCee sections with web openings has not been addressed to date. Hence, this study intends to analyse the shear behaviour of SupaCee sections with web openings. Previous shear test results of SupaCee sections and Lipped Channel Beam (LCB) sections with openings were validated with developed FE models. An extensive parametric study was accomplished considering various geometric parameters such as depth, yield strength, thickness and web opening ratios. Since the results of the detailed study determined that existing design equations were over conservative, new design equations with reduction factor were proposed to predict the ultimate shear capacity of SupaCee sections with web openings. Moreover, the shear capacities of SupaCee sections were compared with shear capacities of similar dimensioned LCB sections. A web opening ratio of 0.2 is recommended, considering the ability to regain the shear capacity of plain LCB sections, as well as the availability of web openings in order to accommodate the services.

Analysis of the effect of variation in open area ratio in perforated multi-V rib roughened single pass solar air heater- Part A

ABSTRACT The effect of variation in open area ratio (β) in multi-V rib roughened single pass solar air heater (SPSAH) is computed in this study. Different perforated plastic ribs are used to develop variations in perforation. Four values of the open area ratio (β) ranged from 0 to 0.31, six values of relative roughness width (W/w) ranged from 2 to 10, and nine values of the Reynolds number (Re) ranged from 2000 to 18,000. These values were under consideration, along with fixed values of other parameters. Optimum values of performance parameters achieved at an open area ratio β = 0.27 with W/w = 6. The optimum range of improvement in Nusselt number ratio (Nu/Nus) and thermo-hydraulic performance parameter (THPP) was 6.33–8.19 and 3.78–5.41, while duct friction ratio (f/fs) was recorded within the range of 3.68–4.78 when compared to the flat channel, respectively. A correlation for Nusselt number and friction factor with varying parameters was also established with ±12% and ±7.5% accuracy, respectively.

The role of cross‐sectional geometry of high‐head gated conduit in oxygen transfer efficiency

AbstractThe concentration of dissolved oxygen is an important indicator of water quality because aquatic life lives on the dissolved oxygen in the water. This can be achieved by using hydraulic structures because of substantial air bubble entrainment at these structures. Closed conduit aeration is a particular instance of this. In the present study, experiments were carried out to investigate the role of cross‐sectional geometry of high‐head gated conduit in oxygen transfer efficiency. In the first part of this study, the role of cross‐sectional geometry of high‐head gated conduit in air‐demand ratio was investigated. In the second part, the role of cross‐sectional geometry of high‐head gated conduit in oxygen transfer efficiency was investigated. Results pointed that the cross‐sectional geometry of the high‐head gated conduit had an important effect on the air‐demand ratio and the oxygen transfer efficiency. Moreover, a design formula was obtained for the conduit having the highest oxygen transfer efficiency relating the oxygen transfer efficiency to air‐demand ratio, Froude number, gate opening, conduit length and gate opening ratio. There was good agreement between the measured and the predicted values. The obtained results will be useful in future modelling processes and aid the practicing engineer in predicting oxygen transfer efficiency of high‐head gated conduits.

Investigation of Using Sky Openness Ratio as Predictor for Navigation Performance in Urban-like Environment to Support PBN in UTM.

One of the causes of positioning inaccuracies in the Unmanned Aircraft System (UAS) is navigation error. In urban environment operations, multipaths could be the dominant contributor to navigation errors. This paper presents a study on how the operation environment affects the lateral (horizontal) navigation performance when a self-built UAS is going near different types of urban obstructions in real flight tests. Selected test sites are representative of urban environments, including open carparks, flight paths obstructed by buildings along one or both sides, changing sky access when flying towards corners formed by two buildings or dead ends, and buildings with reflective glass-clad surfaces. The data was analysed to obtain the horizontal position error between Global Positioning System (GPS) position and ground truth derived from Real Time Kinematics (RTK), with considerations for (1) horizontal position uncertainty estimate (EPH) reported by the GPS receiver, (2) no. of visible satellites, and (3) percentage of sky visible (or sky openness ratio, SOR) at various altitudes along the flight paths inside the aforementioned urban environments. The investigation showed that there is no direct correlation between the measured horizontal position error and the reported EPH; thus, the EPH could not be used for the purpose of monitoring navigation performance. The investigation further concluded that there is no universal correlation between the sky openness ratio (SOR) seen by the UAS and the resulting horizontal position error, and a more complex model would need to be considered to translate 3D urban models to expected horizontal navigation uncertainty for the UAS Traffic Management (UTM) airspace.

Experimental study on the cylindrical oscillating water column device

Wave energy, as a type of high-density renewable energy, has great potential to reduce human dependence on fossil fuels. Integrating wave energy converters (WECs) with mature structures such as breakwaters and offshore wind turbines is a promising concept for wave energy utilization. These technologies reduce the costs of WECs while improving their reliability. In this study, a cylindrical oscillating water column (OWC) device that can be integrated into a monopile-mounted offshore wind turbine (OWT) was experimentally investigated, considering the effects of various parameters including incident wave condition, geometry of the air chamber, and power take-off damping. The results showed that there is an optimal wave condition to maximize the capture width ratio (CWR), regardless of whether the maximum pneumatic power is obtained. A shallow submerged depth of the opening promotes energy extraction under a wider band. The results also illustrated that the optimal opening ratio between the cross-sectional areas of the orifice and air chamber is approximately 1.25%, and when the dimensionless wave frequency is less than 2.4, the CWR increases with the radius of the air chamber. This study provides experimental data with which to validate the numerical models developed for OWC.

Novel resonance stability criterion for the 2D magnetically levitated servo-proportional valve

The leakage of the pilot stage of the 2D valve mainly depends on the size of its initial opening. According to the Routh criterion, the pilot stage of the two-dimensional magnetically levitated servo-proportional valve (2D-MSP valve) needs to be designed to have certain positive values to increase the damping ratio to improve valve stability, which leads to the leakage flow representing a non-negligible power loss. In order to reduce leakage flow and achieve goal of energy saving, this paper presents a novel resonance stability criterion by considering nonlinear characteristics of the fluid dynamic system. First, the 2D-MSP valve is regarded as a three-way valve-controlled differential cylinder system. Based on the frequency response of the resonance state, the energy conservation method is used to solve the flow “backfilling” area, the motion equation of the cylinder piston (valve spool displacement) and the pressure waveform of the sensing chamber under different opening and pressure amplitude ratio. Then, the analytical expression of the resonance peak amplitude is obtained and the resonance stability criterion is deduced. The result is compared with the Routh stability criterion, which illustrates that the positive openings of the pilot stage can be reduced to one-third of the original value. The prototype valve is then designed and manufactured based on the resonance stability criterion. The dynamic and static characteristics under different system pressures are measured. Experimental results show that the prototype valve is an over-damped system without any overshoot, which has excellent working stability, and its static and dynamic performance can meet the demands of the industry servo-proportional control system. The research work validates the effectiveness of the proposed resonance stability criterion.

Experimental Investigation of Scouring Around Circular Piers with Different Opening Ratios

Experimental Investigation of Scouring Around Circular Piers with Different Opening Ratios

Novel Quasi-Three-Dimensional Modeling of Axial Flux In-Wheel Motor With Permanent Magnet Skew

This paper presents a characteristic analysis of axial flux permanent magnet machines (AFPMMs) for in-wheel electric vehicles. Preferentially, a novel quasi-3-D model is developed for the fast and accurate design of AFPMMs. In electromagnetic field analysis, combined with field reconstruction method, the computation time of 2-D solutions is significantly reduced. With the use of time sweeping of the basis function, only the static finite element (FE) analysis is performed to calculate the air-gap flux distribution at the entire rotor position, whereas the conventional 2-D solutions require a transient FE analysis. In the shape sweeping process of the basis function, the virtual air-gap section method is introduced to take into account that the ratio of slot opening to slot pitch is different depending on the radius of analysis plane, which causes errors in the analysis results of the conventional quasi-3-D method. The virtual air-gap sections are obtained by interpolation of the spatial field between the mapped cylindrical planes. The proposed technique reduces the number of 2-D analysis planes required for high accuracy in the conventional quasi-3-D method, and it can also predict the air-gap magnetic flux distribution for skewed permanent magnets without additional FE analysis. Finally, using the magnetic fields calculated in the proposed method, the electromagnetic performances of the AFPMM are calculated, such as load torque, cogging torque, attraction force, and back-EMF. The analysis results were verified by comparison with the measurement results.

Effect of Open Area Ratio on Vortex Behavior of Plain Weave Wire Mesh Wake

The wire mesh has a rectifying effect, and the parallel two-sided grid has a turbulent effect. This each effect is a fully developed area, and the transition process to that region has not been clarified. The purpose of this experiment is to clarify the transition process of the wire mesh wake. As the result, it was shown that there is a locally fast secondary flow in the wire mesh wake with the large open area ratio and that the direction of the secondary flow is different. It is considered that the structure of this secondary flow affects the rectification effect.

Attenuation characteristics of Karman vortex passing through the wire mesh

In this study, the attenuation and frequency characteristics of the Karman vortex passing through the wire mesh was investigated. This experiment was conducted by generating the Karman vortex from a cylinder in an acrylic duct of the blowdown type wind tunnel and passing through the wire mesh at the duct exit. The cylinder with a diameter of 6mm was used to generate the Karman vortex, and the Reynolds number was 3000 based on the flow velocity toward the cylinder and the cylinder diameter. The wake of the Karman vortex passing through the wire mesh was measured by hot-wire anemometer, and was visualized by smoke wire method. As a result, it was found that the smaller the wire diameter and open area ratio of the wire mesh, the velocity and turbulence intensity distributions ware more uniform. And, the dominant frequency of the Karman vortex was confirmed that even in the wire mesh that showed uniformity and in the wire mesh that appeared to have collapsed in the photograph by frequency analysis.

Experimental investigation of the effects of contraction on tsunami-induced forces and pressures on a box section bridge

Many bridges that lie within possible tsunami inundation zones are critical links in transport networks. Some efforts have been made to determine the effects of tsunamis on bridges, but only a limited range of published design guidelines are available. Therefore, it is necessary to further investigate the effects of tsunamis on bridges. In the current study, physical modeling experiments were carried out to measure bore impact forces and pressures for various tsunami bore strengths on a bridge deck with different abutment types (wing wall and spill-through) and different opening and submergence ratios. The experiments were conducted in a wave flume with dimensions of 14 × 1.2 × 0.8 m (length × width × height), equipped with an automatic gate designed to generate a tsunami bore. The horizontal and vertical forces showed an increasing trend with increasing submergence ratio for both types of abutment. However, the horizontal force showed a decreasing trend as the opening ratio decreased, while the vertical force initially increased as the opening ratio decreased, until it reached a peak value, and then it started to decrease. The overall shapes of the results for both types of abutment are similar, with higher values for spill-through abutments due to their lower energy dissipation rates. Based on the experimental data, empirical equations are proposed for estimation of tsunami loads as a function of opening and submergence ratios.