Rows Of Slots Research Articles

Influence of instability modes on cooling performance in hypersonic boundary layer with slot injection

A combined numerical-experimental investigation is presented with focus on the effects of boundary-layer instabilities and transition on the wall cooling performance in a Mach 5 low-enthalpy flow over a flat plate, with coolant injection achieved through a row of slots. The numerical study has been performed through direct numerical simulation (DNS) of the compressible Navier-Stokes equations, and is supported by results from linear stability analysis (LST) for the considered boundary layer. The experiments have been conducted in the High Density Tunnel (HDT) of the Oxford Thermofluids Institute, and include several blowing ratio conditions of injected air for the same freestream conditions. Surface heat transfer and pressure measurements, film effectiveness measurements, and Schlieren images are presented. The analysis links the wall cooling performance to the growth of imposed unstable boundary layer modes. Results indicate that 2D and 3D unstable modes, pertaining to the class of first instability modes, exist in the laminar boundary layer, and that imposition of these modes at different amplitudes leads to different states of the boundary layer, which we refer to as a perturbed state and a transitional state for medium and high amplitude respectively. As confirmed by comparison with experimental data, the perturbed and transitional states of the boundary layer significantly affect the wall cooling performance, providing an increase of the wall heat flux that results in a reduction of the beneficial effects of cooling.

Transient Hybridization between Different Hemoglobins Detected by Cross Electrophoresis

In this paper, we aimed to introduce a new method in detecting transient hemoglobin (Hb) hybrids. First, electrophoretic pure HbA, HbA2, HbF and HbA1 were prepared by starch–agar mixed gel, and then cross electrophoresis was performed on 2% starch–agar mixed gel. The slow-moving HbA2 samples were added in the front long slots and the fast-moving HbA, HbF and HbA1 samples were added in the back short slots of the gel. These two rows of slots are all located on the cathode side of the gel and about 1 cm away from each other. After electrophoresis, which was performed at 5V/cm for about 4 h, the gel was stained with Ponceau Red and Benzidine. The results showed that when fast-moving HbA and HbF crossed slow-moving HbA2, the band shape of HbA2 was deformed as a valley, however when fast-moving HbA1 crossed slow-moving HbA2, the band shape of HbA2 was not deformed. This finding demonstrates that HbA and HbF could form transient hybrid with HbA2 during cross electrophoresis; however HbA1 could not form any hybrid with HbA2 because of its chemical modification of Hb subunits.

Series-Fed Beam-Steerable Millimeter-Wave Antenna Design With Wide Spatial Coverage for 5G Mobile Terminals

A low-cost beam-steerable antenna operating at 28 GHz is presented for 5G mobile terminal applications. The proposed array has a sandwich-like stack structure, including ten patch elements, a ground plane with two rows of slots, and a long microstrip transmission feed line. The radiators and the transmission line are placed at the two sides of the ground plane, which provides great flexibility in designing the radiating pattern and the feed network. Switches are added on the transmission line to construct periodic distributed phase shifters for beam steering. The 2 bit phase shifter with phases of 0°, 90°, 180°, and 270° is formed without using phase delay lines. Continuous beam steering is achieved, and the steerable angle is 121° in the upper hemisphere. Two location configurations of the proposed array in 5G mobile terminals are analyzed and the angular coverage range is evaluated. The array can cover 38.8% of the hemispherical space with a gain threshold of 10 dBi.

Detailed Flow and Heat Transfer Analyses in a Rib-Roughened Trailing-Edge Cooling Cavity With Impingement

A rig, simulating two adjacent cooling cavities on the trailing side of an airfoil, made up of two trapezoidal channels is tested. Eleven crossover holes on the partition wall between the two channels create the jets. Two exit flow arrangements are investigated—(a) jets, after interaction with the target surface, are turned toward the target channel exit axially and (b) jets exit from a row of racetrack-shaped slots along the target channel. Flow measurements are reported for individual holes and heat transfer coefficients on the eleven target walls downstream the jets are measured using liquid crystals under steady-state conditions. Smooth as well as ribbed target surfaces with four rib angles are tested. Correlations are developed for mass flow rate through each crossover hole, varying the number of crossover holes. Heat transfer coefficient variations along the target channel are reported for a range of 5000–50,000 local jet Reynolds numbers. Major conclusions are: (1) Correlations are developed to successfully predict the air flow rate through each crossover hole for partition walls with six to eleven crossover holes, based on the pressure drop across the holes, (2) impingement heat transfer coefficient correlates well with local jet Reynolds number for both exit flow arrangements, and (3) case of target channel flow exiting from the channel end, at higher jet Reynolds numbers, produce higher heat transfer coefficients than those in the case of flow exiting through a row of slots along the target channel opposite to the crossover holes.

Fire performance of non-load-bearing light-gauge slotted steel stud walls

Experimental and numerical studies on the performance of light-gauge slotted steel stud walls subjected to fire are presented in this paper. Four full-scale light-gauge slotted steel stud walls were tested under the ISO-834 standard fire loading. Temperatures at the location of exposed surface, unexposed surface, and cross section of steel studs were measured. Spalling of the heated gypsum board during testing was investigated. The major factors affecting the behavior of this type of wall, including the height of the web, layers of gypsum boards and use of mortar on unexposed surface, were studied.Based on the test results, a three-dimensional FE model of the light-gauge slotted steel stud wall was developed using ABAQUS to analyze its fire performance. The model was validated against experiments in this study and other related test data. The FE model was employed to conduct further parametric studies. Parameters include the spalling time of heated gypsum boards, the height of the web, rows of slots, and layers of gypsum boards. The effects of these key factors on the temperatures of the exposed surface, unexposed surface and studs are discussed.

Periodic leaky-wave antennas fed by a modified half-mode substrate integrated waveguide

This study presents two configurations of periodic leaky-wave antennas fed by a modified half-mode substrate integrated waveguide (HMSIW) where a metallised trough is employed as the waveguide's side wall. The first antenna configuration is constructed from periodically etching a row of transverse slots on the ground plane of the feeding HMSIW, whereas in the second configuration, the row of slots is cut into the HMSIW top wall. Influence of the slot length and period on the propagation constant of the fundamental space harmonic is quantitatively characterised through analytical equations, simulations and measurements of fabricated prototypes. This provides essential information towards the synthesis of more sophisticated HMSIW-fed leaky-wave antennas. The performance of the two prototypes demonstrates forward-to-backward radiation within the mono-mode regime of the feeding HMSIW. The agreement between the theoretical, numerical and experimental results validates both the overall analysis procedure and the concept of periodically slotted thru HMSIW as leaky-wave antennas.

Multilayer panel with an improved noise damping

The acoustic characteristics of lightweight multilayer construction panels have been improved by the formation of three-dimensionally meandering curved slots or rows of slot sections in the core of the panels. The slot depth varies along the length of the curved slots. The slots or rows of slots are spaced from each other by an on-center spacing that is preferably constant along the length of the slots.

Testing sequence effects in visual memory: clues for a structural model

In order to probe the internal organization of visual temporary memory, systematic experiments were performed in which the subjects had to memorize a series of 2–5 images then pass recognition tests, either in all possible testing permutations, (in the case of 2–4 images) or in 20 selected permutations (in the case of 5 images). Over 300,000 tests were performed, generating more than 40,000 errors. The error-rates were found to follow simple rules. Both the 3 and the 4 images results are compatible with the presence of only four typical accuracy levels. On the other hand, the reaction time (RT) results revealed surprisingly rich patterns. The RT for recognizing image i at testing stage t>1 depends upon which image ( j) was tested just before. The ranking of the RTs for ( j, i) couples evolves from one testing stage to the next. It is proposed that these RTs reflect, in part, the time needed to localize the trace in memory of a given image, starting from the position at which the previous test occurred. If this assumption is correct, the results of this study are providing a picture of the configurations formed by memorized items in the visual temporary store. A hypothetical minimal model, involving several rows of slots on a triangular mesh is proposed to account for the structures in both the error-rates and the RT results.

Unsteady-State Pressure Response Due to Production With a Slotted Liner Completion

Summary The transient behaviour of production from a well with a slotted liner has been solved analytically by the source function method. The unsteady-state pressure response was examined as a function of slot frequency and slot pressure response was examined as a function of slot frequency and slot length, with a penetration ratio of 1:2. The results indicate that limited entry into the well causes skin effects. However, the effects become negligible when three or more slots are distributed around the circumference of the liner. For more than three slots, the well effectively behaves like a continuous-surface cylindrical source (or a line source well, depending on time and location). We conclude that there is likely to be little reduction in flow efficiency in an ideal slotted liner completion, unless some slots are clogged. Introduction A well is completed with a slotted liner when sand problems occur, mainly in unconsolidated formations. The slotted liner is a preperforated tubing. Usually, the slots are milled and machined in vertical rows, parallel to the axis of the pipe. The most common patterns of slot arrangement are staggered vertical, multiple staggered vertical, and horizontal (Fig. 1). Standard spacing of slots is 6 in. between the slots in each vertical row, while their length is usually 1 1/2 to 2 in., depending on their width. The common practice is to specify two rows for each inch of nominal pipe diameter. An analytical solution to the problem of transient pressure response due to production through a liner with staggered vertical rows of slots was found. The technique used was the source function method suggested by Gringarten and Ramey. It applies the use of a line source of finite length that in turn represents one of the systems of slots. The solution technique was verified by comparison with the continuous-surface cylinder solution in the case of a large number of vertical rows of slots. No storage or damaged zone effects were considered. Problem Description Problem Description Consider an infinite, homogeneous, and isotropic porous medium. The transient (unsteady-state) flow of a slightly compressible fluid is governed by the diffusivity equation ............................(1) where = is the diffusivity term. The solution to a particular problem is determined by the initial and boundary conditions. One of the problem is determined by the initial and boundary conditions. One of the most well-known solutions is Kelvin's instantaneous point source function, ............................(2) Eq. 2 represents the pressure drop created at Point M in a reservoir of infinite extent by an instantaneous point source of strength q at Point P, distance d from Point M (Fig. 2). JPT p. 1366

Month in the Patent Office

The inner wall 10 of a gas‐turbine diffuser is formed with two rows of circumferential slots 40, 42 whereby, due to the increasing static pressure in the downstream direction, gas will flow into the downstream slots 42 and out of the upstream slots 40 to set up a circulation which will energize the boundary layer to increase its flow in the same direction as the gas stream. The rows of slots are staggered circumferentially but do not overlap axially. In an alternative arrangement the slots are formed in the outer wall of the diffuser, an external U‐shaped member surrounding the slots to provide an annular circulation chamber.