Single Splitter Research Articles

Numerical Study of Vortex Effect on Splitter Plate under Turbulence Flow over Circular Cylinder

Vortex shedding is commonly observed in both natural and artificial situations. Two key variables, the blockage ratio and the Reynolds number, determine the flow characteristics around a confined bluff body. The goal of the current study was to apply numerical simulation to examine the development of vortices in a continuous turbulence flow at the distanced position of a single splitter plate. As a starting point, the flow around a fixed circular cylinder and plate is examined at various spaced position ratios, where *L ratios are defined as the distance between the cylinder's centre and the plate's front edge. In the wake of the cylinder, when *L is raised, positive and negative vortices are generated. The pressure distribution following the vortex sheddingcore strike is felt at the plate face tip (starting edge). Compared to the other two positions, the CL created by L2 is larger and receives better cortex hits.

Study on the parameters of detached dual splitter plates and comparison with single plate for VIV suppression

In the actual marine engineering environment, vortex-induced vibration will affect the safety of cylindrical structures. Rigid splitter plates have become one of the suitable VIV suppression solutions due to their simple structure and low maintenance costs. Therefore, on the basis of numerical simulation, this paper analyses the influence of the gap between parallel and non-parallel double splitter plates and the arrangement angle of non-parallel double splitter plates on the VIV suppression effect at a fixed flow rate. In addition, the VIV suppression effect of the single and dual splitter plates with the same parameter combination is evaluated under the condition of multi-flow velocity. It is found that the parallel dual splitter plate cannot provide good VIV suppression, especially when the gap exceeds the cylinder diameter, the suppression effect begins to deteriorate. However, on the basis of a certain gap between the plates, the dual splitter plate with arrangement angle is more effective than the single splitter plate in suppressing the transverse vibration of the cylinder. Therefore, when using dual splitter plates for VIV suppression, the parallel dual splitter plates should be avoided. When a better transverse vibration suppression effect is required, the arrangement angle can be appropriately changed.

Wake control of a square cylinder: Impinging the vortex cores with dual flexible splitter plates

Numerous works have been conducted to study the wake control of a bluff body and more efficient strategies are still what we seek for. This paper studies the complex fluid–structure interaction (FSI) problem of a square cylinder mounted with dual flexible splitter plates from a new perspective: impinging the vortex core with flapping plate tip. The Reynolds number (Re) based on the side length of the square cylinder is fixed at 332.6. The splitter plates are attached at both sides of the square cylinder. Structural parameters, such as plate length and bending stiffness, are considered to achieve an optimal arrangement of this configuration. Compared to the traditional single splitter plate arrangement, only a short splitter length is needed for this dual splitter plates configuration. Flow visualization indicates that the drag reduction is associated with the increase of base pressure and the lift suppression is related to the inhabitation of the interaction of the shear layer and split effect of the tip vortices. The dimensionless bending stiffness plays a vital role in determining the behavior of the splitter plate. Two vibration modes, i.e., off-center vibration and asymmetry vibration modes are captured and the up and down splitter plates tend to vibration in-phase. The Lissajous trajectories of the free tip mainly exhibits arc-shape and sickle-shape. Given the performance of the square cylinder-dual splitter plates configuration, splitter length of l/L=1.5 is an optimal configuration, which is less affected by flexural rigidity. The maximum drag reduction could reach 23.1% and the lift force exerting on this configuration does not increase significantly, which is beneficial for the structural stability.

Studi Numerik Pengaruh Penggunan Splitter Plate Terhadap Sifat Aliran di Sekitar Penampang Persegi

The phenomenon of the movement of fluid flow across an object plays an important role in terms of transportation. Different body shapes will produce different fluid flow characteristics and greatly affect the function of the body shape, so it is important to know the characteristics of fluid flow, so that the factors causing losses in a construction that are not in accordance with the natural properties of the fluid can be identified. If the drag is large can be reduced, the energy needed to move can be reduced and save fuel. the use of numerical methods is a way of studying flow characteristics that is relatively inexpensive with a scientifically justifiable level of accuracy. The problem of this study is how the characteristics of the fluid flow to the forces that pass through the square cross section. This study uses a square geometry test model and a single splitter plate geometry test. The research was carried out by computational methods using Ansys FLUENT CFD software with the Realizable k-ε turbulence model. The results showed that the use of a splitter plate resulted in a decrease in Cd, -CPb values and an increase in speed (u). This indicated that the use of a splitter plate could reduce resistance and pressure and expedite the distribution of fluid flow. and there is an increase in the Cl value parameter, this is due to the enlargement of the wake. From this study it was found that the use of a splitter plate was good in reducing Cd values, this is in accordance with the literature
 Kata kunci: Ansys fluent, CFD, fluid, Reynolds, drag coefficient, pressure coefficient, lift coefficient

Induced roll magnetic separator applied for high grade ilmenite separation from mining tailing

This article aimed to separate ilmenite (FeTiO3) mineral from tin tailing applying a single splitter IRMS (Induced Roll Magnetic Separator). Ilmenite mineral is the substantial main source for TiO2. This work used air table middling for feeding. The mineral components of middling feeding from air table using grain counting analysis were found as follows: cassiterite (48.61%), ilmenite (21.36%), monazite (18.56%), pyrite (4.60%), zircon (5.85%), quartz (0.71%), anatase (0.27%), and tourmaline (0.02%), It was found that electrical current and opening of single splitter affected the degree of separation addressing to ilmenite recovery and ilmenite grade. The finding showed that current of 15 Ampere and single splitter with opening 4.25 cm yielded ilmenite recovery more than 74%. The high grade ilmenite (90.46 %) and recovery of 29.38% was obtained using 5 Ampere with single splitter opening of 1.0 cm. Up to date, the study on ilmenite separation from tailing only focused on the effect of current, however, the effect of single splitter magnetic separator to enhance ilmenite recovery from other paramagnetic minerals such as monazite, siderite, xenotime and tourmaline has not yet been reported.

Backward-Wave Oscillation Suppression in Folded Waveguide Traveling-Wave Tube With Metamaterial Absorber

A D-band folded waveguide (FWG) traveling-wave tube (TWT) with metamaterial absorber (MMA) is proposed, where the MMA is designed to suppress the backward oscillation in this FWG-TWT. The MMA consists of single splitter rings (SRs) with silica layer that adheres to the inner surface of a metallic waveguide. The absorption frequency of this MMA is well designed to cover the backward frequency of FWG slow wave structure (SWS). Therefore, this MMA achieves the transmission of forward wave and the attenuation of backward wave, which improves the performance of FWG-TWT. Simulation results show that 66.1 W saturated output power driven by 5 mW 150GHz input signal, with a corresponding gain of 41.2 dB, and a bandwidth of 18 GHz with output power greater than 40 W can be achieved with 90 periods SWS. The proposed FWG-TWT with MMA may provide a high gain for high frequency amplifier, where it is helpful to design an FWG-TWT with low input power.

Effect of blade layout on performance of low specific speed pump operating in turbine mode

The very low specific speed pump (nq = 8.9) operated in turbine mode was analyzed. The experimental and numerical studies were carried out in order to show effect of different blade layout on pump-as-turbine (PaT) performance. In total three different impellers were analyzed. One impeller consisting of four main blades and two impellers consisting of four main blades and different arrangement of splitter blades. Either single splitter blade or two splitter blades are placed between each of main blades. While measurements pointed out the main PaT performance, the simulations enable to analyze internal flow fields and point out the mechanisms of performance variation using different impellers. The main aim of this study is to clarify usability of very low specific speed pump for energy recovery in terms of pump as turbine operation or for storage capability in terms of pump-turbine.

Experimental investigation on flow-induced vibrations of a circular cylinder with radial and longitudinal fins

Flow-induced vibration (FIV) of a heat exchanger tube may present both negative effects (e.g., causing fatigue damage of the tube) and positive effects (e.g., enhancing heat transfer efficiency). As a typical passive control approach, fins attached to the tube (or circular cylinder) present significant effects on its FIVs. This study carried out systematic wind tunnel tests to investigate the FIVs in the transverse direction (along with the drag forces) of a circular cylinder with various radial and longitudinal fins. For the radial group, 3 cases with spare, moderate, and dense fins were tested. For the longitudinal group, 24 cases with various fin numbers and arrangements were tested. For the longitudinal fin arrangement parallel to the flow direction (also known as a circular cylinder with single or dual splitter plates), various fin lengths were also tested. The experimental results showed that a radial finned cylinder always presents larger FIVs than a bare circular cylinder. The longitudinal fins may significantly increase or decrease the FIVs depending on the number and arrangement of attached fins. For example, a single splitter plate (placed either upstream or downstream of the circular cylinder) often increases the FIVs, while dual splitter plates with large lengths can effectively suppress the FIVs. The experimental results provide valuable guidance for selecting appropriate fin configurations to passively control the FIVs to a certain level that can enhance the heat transfer efficiency without introducing unacceptable fatigue damage.

Competitive light beam splitters based on complex interference wedged structures that use low-reflectivity components (Fresnel reflection)

We demonstrate that interference wedge structures suitably composed of wedged purely glass elements using Fresnel reflection only can be effectively employed for realization of competitive light beam splitters and filters (especially for high-power laser beams). The theoretical analysis, simulation and experimental testing show that for appropriately chosen parameters and for a suitably composed interference complex such structures can achieve a controlled variable transmission in a wide range (99% – ∼30%) and reflection from ∼2% to ∼70%. The traditional realization of purely glass splitters ensures no more than ∼20% reflectivity. The splitters proposed are very compact sheet-like elements (e.g., 5×3×0.2 cm) and the splitting is implemented by sliding in the splitter’s plane. Thus, the propagation direction of the formed beams is preserved. The incident beam on the purely glass splitter (no dielectric or metallic mirrors) can be of high power and the influence of the air humidity is strongly reduced; also, cleaning the filter surfaces presents no difficulties. A single splitter can work in a wide range of wavelengths (IR, visible) without polarization dependence for incident angles up to ∼20°.

A numerical study on the enhanced drag reduction and wake regime control of a square cylinder using dual splitter plates

In this paper, a dual splitter plate flow separation control device is introduced for a low Reynolds number flow (Re = 100) around the square cylinder of length L to achieve higher drag reduction and improved wake regime control compared to the conventional single splitter plate control devices. Here, two splitter plates of the same length W (ranging from 0.25 L to 2.50 L) are symmetrically attached on the rear surface along the horizontal centerline of the square cylinder with a spacing H (ranging from 0.0 L to 1.0 L) between them. The numerical study is performed using the in-house developed flexible forcing immersed boundary-lattice Boltzmann solver [1] to investigate the effects of dual splitter plate on the flow regime and flow-induced forces. The shear layer interaction with the splitter plates, as well as the vorticity and pressure distribution in the near wake region, are significantly modified by varying W and H, and four different flow regimes (Type I to Type IV) are identified from the observations. Among these flow types, the Type III flow pattern displays an accelerating flow in the wake region that is found to be most beneficial for higher base pressure recovery and drag reduction. Furthermore, dual splitter plates suppress von-Karman vortex shedding and lift force fluctuation, and produce higher drag reduction (≈ 21%) at less than half of the plate length of a single splitter plate. It is also noticed that a dual splitter plate configuration seems to be an optimum arrangement, since adding more splitter plates (up to 5 numbers were tested) on the rear surface of the square cylinder does not change the wake characteristics nor shows any improvements in the drag reduction.

Logic Optimization, Complex Cell Design, and Retiming of Single Flux Quantum Circuits

Single flux quantum (SFQ) technology has emerged as a promising beyond-CMOS technology with Josephson junctions (JJs) as active devices in a superconducting circuit. In this paper, we (i) describe the algorithms and the methodology we used to synthesize a synchronous SFQ circuit using a CMOS logic synthesis tool by adding new features to the tool and by modifying the existing features; (ii) introduce the concept of two kinds of complex cells: (a) stand-alone cells and (b) interconnected cells along with the advantage gained by these complex cells through the results of synthesized SFQ netlists. Design of stand-alone complex cells presented here includes and and or gates with more-than-two inputs, high-fanout splitters, and “A+BC” cell. Circuits of decoders, multiplexers, and carrylook-ahead adders are synthesized with complex cells, and the advantage in terms of JJ count and latency is presented. We have also investigated the possibility of SFQ cells supporting multiple fanout drive capability by modifying the input/output interfaces of SFQ standard cells. In this direction, an algorithm to modify the input interface of a cell so that it can be driven along with similar cells by a single splitter output is presented along with the results for a simple clock-distribution line with multiple-fanout capability.

Effects of the impeller–volute tongue interaction on the internal flow in a low-specific-speed centrifugal pump with splitter blades

To investigate the effects of the main blades and splitter blades interacting with the volute tongue on the internal flow in a low-specific-speed centrifugal pump, the Reynolds-averaged Navier–Stokes equation, coupled with SST k-ω turbulence model, is employed to simulate the transient turbulent flow in the whole flow passage. The numerical simulation results have been verified with the experimental measurements by comparing the head and efficiency. The pressure fluctuation caused by impeller–volute tongue interaction, including time–history and frequency characteristics, is calculated and analyzed at five monitoring points adjoining the impeller outlet and tongue, as well as the torque of a single main blade and a single splitter blade. After that, both the energy loss and vorticity distributions on the middle section are discussed when the impeller rotates to four circumferential positions relative to the cutwater. The results show that the maximum pressures at the monitoring points occur before the blades reach the closest circumferential position with respect to the cutwater, and the peak pressure near the trailing edge of splitter blades is larger than main blades. There is only one torque peak of a single blade in one revolution when the angle between the monitoring blade and tongue is about 15°. Additionally, the torque peak arises before the torque valley, but the pressure valley at monitoring points in the impeller comes earlier than the pressure peak. Both the energy loss and vorticity are enlarged around the volute tongue evidently after the blades pass by the cutwater, and the splitter blades produce more unsteadiness and energy dissipation than main blades.

Effect of arrangement of inline splitter plate on flow past square cylinder

Two-dimensional numerical study has been carried out to investigate the effect of the presence of a single splitter plate in upstream location, and presence of two splitter plates, in upstream as well as downstream locations, for low Reynolds number incompressible flow past a square cylinder. Using finite difference discretisation and MAC algorithm, an indigenously developed computational code has been used for solution of the governing flow equations. The length of the plate and its position do play good role in controlling the flow past the cylinder. The difficulty lies in identifying an optimum configuration of these parameters. The length of the attached splitter plate as well as separation of the detached splitter plate of fixed length are varied for both the upstream and downstream configurations up to maximum Reynolds number of 200. To begin with, the effect of upstream splitter plate alone in attached as well as detached configuration is studied with an aim to identify the optimum configuration associated with reduced drag as well as delayed onset of vortex shedding. Then, for the optimum configuration of the upstream plate, the effect of downstream plate on flow characteristics and critical Reynolds number for onset of vortex shedding has been studied.

The passive control of wake flow behind a circular cylinder by parallel dual plates

In this paper, the wake control of a circular cylinder by dual plates symmetrically attached at the rear surface is numerically investigated within the laminar flow regime. The two flat plates are arranged in parallel form, and the attachment angle is varied in the range θf=0–90°. In comparison to the use of a single splitter plate, the dual plates cause increased drag reduction and stronger wake suppression at relatively shorter plate lengths. It is shown that the attachment angle has a crucial effect on the control efficiency, and the most effective range associated with the maximum drag reduction is between 40°≤θf≤50°. Within this regime, the free shear layers reattach on the outside surface of the control plates. The potential mechanism responsible for the wake control is suggested based on a comparison with other passive control configurations.

0315 遷音速遠心圧縮機のサージング点近傍における羽根車流れに及ぼすマッハ数の影響(OS3 流体機械の研究開発とそれに関連した複雑流動現象,オーガナイズドセッション)

In order to improve the performance and operating range of centrifugal compressors, it is indispensable to understand unsteady behavior of vortical flows. In this study, the flow fields at different rotational speed in a transonic centrifugal compressor with single splitter blades have been investigated by Detached Eddy Simulation(DES). The simulation showed that the detached shock wave ahead of full blade, which interacts with the tip leakage vortex as well as the suction surface of adjacent full blade, became strong with a rise in rotational speed, so that the shock wave caused the tip leakage vortex breakdown in almost all pitches. Moreover, it was found that early occurrence of the vortex breakdown at higher flow rate led to a reduction in operating range.

Suppression of wake-induced vibration of tandem cylinders with free-to-rotate control plates

Experiments have been carried out on a pair of circular cylinders to investigate the effectiveness of pivoting parallel plates as wake-induced vibration suppressors. Measurements of amplitude of vibration and average drag are presented for a circular cylinder, free to respond in the cross-flow direction, with mass ratio 2 and a damping level of 0.7% of critical damping. Reduced velocities were up to nearly 30, with associated Reynolds numbers up to 2.3×10 4 and the results presented are for a centre-to-centre separation of cylinders of 4 diameters. It is shown how vortex-induced vibration and wake-induced vibration of the downstream cylinder of a tandem pair can be practically eliminated by using free to rotate parallel plates. The device achieves vibration suppression with a substantial drag reduction when compared to a pair of fixed tandem cylinders at the same Reynolds number. Results for a single splitter plate and helical strakes are also presented for comparison and were found not to be effective in suppressing wake-induced vibration.

Frequency Selection Mechanism of Airfoil Trailing-Edge Noise

DOI: 10.2514/1.45138 An experimental investigation was conducted with the aim to reveal the frequency-selection mechanism of the acoustic noise emanated from the trailing edge of two-dimensional airfoils, and a single splitter plate was proposed for suppressing trailing-edge noise. It was observed that broadband disturbances caused by Tollmien–Schlichting instabilities in the transitional boundary layer increase if trailing-edge noise is suppressed with the proposed device. Inaddition, bythe introduction of artificial acousticfeedback, forwhich the initial disturbances are obtained froma sensorforunsteadypressure nearthe trailingedge, aparticular discrete Tollmien–Schlichting waveis selectedfrom among the broadband disturbances caused by Tollmien–Schlichting instabilities. This result demonstrates that the process of frequency selection is clearly ascribable to a positive feedback loop between instabilities in the boundary layer and trailing-edge noise. Also, the application of artificial acoustic feedback shows that the airfoil boundary layer favors a particular frequency, which results in steplike structures as a function of the distance between the loudspeaker and the trailing edge that are similarly observed in conventional environments with natural trailingedge noise emission. Nomenclature Cp = pressure coefficient c = chordwise length of the model f = frequency l = distance between the trailing edge of the model and the microphone or loudspeaker s = length of the splitter plate U = mean velocity in streamwise direction u = fluctuating velocity in streamwise direction x = distance in streamwise direction y = distance in the direction normal to the model surface z = distance in spanwise direction � = angle of attack � = angle between wing centerline and microphone or loudspeaker � � = displacement thickness of the boundary layer