Inlet Channel Research Articles

The tidal prism as a dynamic response of a nonlinear harmonic system

As known, the empirical relationship between the equilibrium cross-sectional area of a lagoon inlet and the tidal prism was intuited for the first time by LeConte [“Discussion on the paper, “Notes on the improvement of river and harbor outlets in the United States” by D. A. Watt,” Trans. ASCE 55, 306–308 (1905).] and then formalized by O'Brien [“Estuary tidal prism related to entrance areas,” Civ. Eng. 1(8), 738–739 (1931)]. This relationship requires knowledge of the tidal prism, which can be estimated either using the cubature method or the current data method [Jarrett, Tidal Prism-Inlet Area Relationships (Coastal Engineering Research Center, US Army Corps of Engineers, Fort Belvoir, VA, 1976)], both of which involve the execution of a number of experimental measurements. However, these methods, besides being very expensive, can only provide the prism value in the present condition and do not allow for predictions in the case of significant morphological changes, of both natural and anthropic origin, to the tidal inlet. On the other hand, the hydrodynamic relationship, which links the tidal prism to the product of the tidal range and the basin extension, can only give a coarse estimate of the prism, especially when the value of the tide outside the lagoon is considered. In this work, we propose a simple hydrodynamic relationship based on the dynamic response of a nonlinear harmonic system. This is a relationship that requires the calibration of a single physically based parameter. Through this relationship, knowing the geometric characteristics, the bottom friction of the inlet channel, the surface of the basin, and the tide amplitude in the open sea, it is possible to estimate the tidal prism. The application of this relationship to real cases shows a good agreement with the experimental data.

РЫБОХОДНО-НЕРЕСТОВЫЙ КАНАЛ В СОСТАВЕ КОЧЕТОВСКОГО ГИДРОУЗЛА НА Р. ДОН

Purpose: development of a layout and design solution for a fish passage and spawning channel, arranged as a part of the Kochetovsky waterworks on the river Don. Materials and methods. The factual basis of the development was made up of known information and materials of complex authors’ surveys and studies carried out at the Kochetovsky waterworks according to generally accepted methods. Results. When developing a technical solution for a fish passage and spawning canal, scientific and technical information on the layout and design of the hydraulic structures of the existing Kochetovsky waterworks, data on the hydrology and hydrometry of the investigated section of the river, topographic and other materials were collected, processed and analyzed. It is proposed to contour the canal bypassing the waterworks structures within the right-bank water protection zone of the river with the inclusion of: an inlet head equipped with a mating flume and an additional power supply unit; canal track of a curved shape in a plan, equipped with recreation areas for fish; outlet head with a head regulator that performs the function of the main power unit. A channel arrangement with the following characteristics is proposed: the total flow rate at the fish entry to the channel is 90 cubic m/s; channel track flow rate, provided by the head regulator, 50 cubic m/s and the consumption of an additional power supply unit of 40 cubic m/s; the average water flow velocity in the non-flooded zone of the channel tract is 0.95 m/s; channel inlet flow rate 0.60–1.05 m/s; water depth in the unflooded zone of the canal tract 2.5 m; channel width (trapezoidal section) along the bottom 15.0 m; slopes gradient 2.5; channel length 5850 m. Conclusion. A layout and design solution for a fish passage and spawning canal, arranged bypassing the Kochetovsky waterworks facilities (river Don), organically adapted to the conditions of its creation and providing conditions for passing and spawning of anadromous fish species, has been developed.

Heat Transfer Coefficient Calculation for Developed Ammonia Boiling in the Evaporator Channel of a Thermal Sink

The subject of this article is the heat transfer of ammonia in the channels of thermal sink evaporators. The objective was to determine a sufficiently simple correlation acceptable for engineering practice, which could be used to calculate the heat transfer in cylindrical channels of a thermal sink, designed for two-phase systems of thermal control systems of uncrewed spacecraft. For this purpose, experiments were performed on two thermal sink having an evaporator channel of ~7 mm diameter made of aluminum alloy and stainless steel, with channel surface roughness Ra 3.33 µm and 0.12 µm. The experiments were carried out with a subcooled liquid or two-phase flow at the channel inlet. The results of the experiments were compared with Kupriyanova's formula obtained under markedly different conditions: with ammonia boiling in a large volume on the external surface of 5...6 mm diameter tubes at –40 °C...+20 °C. It is shown that Kupriyanova's formula can be used on the ground and in microgravity conditions to calculate heat transfer coefficients during the developed boiling of ammonia in the range of flow parameters: saturation temperature +35 °C...+75 °C; mass velocity 27...200 kg/(sec-m²); liquid subcooling to saturation temperature at thermal sink inlet 0 °C...30 °С; mass vapor quality at the inlet 0...0.7. Difference of calculated and experimental values of heat transfer coefficients did not exceed 30 %.

SUBSTANTIATION OF ENERGY-POWER PARAMETERS OF THE STEEL LADLE SLIDE GATE CATAPULT

The theoretical and experimental studies were performed in the design and energy-power parameters of the catapult, which is part of the steel ladle slide gate and ensures the destruction of the crust, which often forms in the surface layer of the loose starting mixture at the inlet of the outlet channel and prevents the beginning of the free outflow of liquid metal when the ladle tundish is first opened. A method was proposed for calculating the dimensions of flat elastic elements of a catapult, taking into account the dimensions of slide gates installed on the steel casting ladles with a capacity of 100–300 tons, as well as the strength of the resulting crust. The obtained calculated dependences are based on the law of conservation of energy of the studied catapult system. It is shown that its use would eliminate the need to use oxygen for burning the solid bulkhead and thereby eliminate the intense destruction of the working walls of the steel outlet channel, contamination of the cast metal with exogenous inclusions and violation of the required velocity mode of its flow from the ladle. Compared with known foreign analogues, the proposed catapult favourably differs in its simple design, low cost, low operating costs and reusable application. This is achieved by moving its power unit out of the steel outlet channel of the ladle gate

Study of density wave instability in natural circulation with parallel channels under inclined and heaving conditions

Nuclear reactors used in warships, commercial ships and floating nuclear power plants will move synchronously with the carrier due to the action of waves or surges. Under ocean conditions, flow oscillations due to additional external motions can be superimposed with flow instabilities in the system resulting in larger amplitude oscillations or even resonances. Sustained compound oscillation will lead to fatigue failure of components, deteriorate local heat transfer, and affect the safe operation of the reactor system. The PNCMC (Program for Natural Circulation under Motion Condition) program is utilized in this research to explore the density wave instability (Type-I) in parallel channels during ocean circulation, and stability boundaries under different thermal-hydraulic parameters as well as ocean conditions to support the safe operation of the system. Through our study, it is found that under the condition of small heating channel inlet resistance coefficient, the unstable boundary powers in vertical case of natural circulation according to the order from small to large are the initial boundary of the parallel three-channels out-of-phase oscillation, the initial boundary of system's density wave oscillation, the boundary of the terminated system oscillation of density wave, as well as boundaries of three parallel channels where out-of-phase oscillations terminate, respectively; The inclined condition's stable boundary is generally lower than that in the vertical case. Unstable boundary power for the natural circulation in the heaving situation according to the order from small to large are the initial boundary of density wave oscillation in whole system are the initial boundary of oscillation of the density wave in system, the initial boundary of the parallel three-channels out-of-phase oscillation, boundary for three parallel-channels where out-of-phase oscillations terminate, and the boundary of the terminated system density wave oscillation, respectively; The oscillations caused by heaving motions, the system oscillations of density wave, as well as oscillations out of phase between the channels were overlapped to cause flow oscillations of very complex compound inside the heating parallel channels. At the same time, the increase of the resistant coefficient at inlet of heating channels can significantly suppress out-of-phase oscillation between the channels.

Numerical simulation of the inlet channel geometry influence in the torque generated at the gravitation water vortex turbine

The gravitational water vortex turbine is presented as an alternative for electric power generation for both low head and water flow conditions, additionally it is easy and low cost to implement and maintenance. However, the experimentally reported efficiencies motivate the scientific community to develop new geometries in order to improve its performance. First, it is not clear how the efficiency of the turbine is obtained and second, not all studies report it. The turbine is mainly made up of a tank, the rotor and the electric generator. The geometry of the tank is important because it stabilizes the fluid and in this component that the generation of the vortex is induced, which determines, added to other factors like tank geometry and runner, the global efficiency of the turbine. The primary purpose of this study is to compare numerically the torque generated at six (6) geometrical configurations of the basin inlet channel for Gravitational Vortex Turbine (GVT) with a Savonius rotor. The study was developed in ANSYS® CFX, where a transient state VOF model was configured with a BSL K − ω turbulence model and a discretization a discretization of the control volume made in the ICEM module. The highest torque was 0.553 Nm at 25 rpm for the trapezoidal curved inlet channel geometry, increasing the efficiency respect to the conventional Square inlet channel of the 2.73 %. The increase of tangential velocity contributes positively to the vortex generation, and consequently, an increase in torque is obtained. On the other hand, the design of the rotor considerably affects the performance of the GVT, where it may or may not take advantage of the kinetic energy of the vortex

Surrogate modeling method for multi-objective optimization of the inlet channel and the basin of a gravitational water vortex hydraulic turbine

This work presents a high-fidelity surrogate model for generating a multi-objective genetic algorithm to allow the search for the optimal geometry of the inlet channel and the basin of a gravitational water vortex hydraulic turbine. Six parameters were considered for the optimization: the relations between the basin diameter (D) and the basin height (H), H/D; the wrap-around angle (γ), the outlet diameter (d) and D, d/D; the inlet channel width (w) and D, w/D; the inlet channel height (h) and D, h/D; and the inlet channel length (L) and D, L/D. Two conflicting objectives were studied: maximizing the vortex strength (Γ) and minimizing the volume flow rate (Q). The multi-objective optimization problem was resolved by applying the gamultiobj function in Matlab R2018b software. The optimization combines the genetic algorithm with Kriging interpolation to obtain the Pareto front. To train the gamultiobj function, an initial population of 40 individuals was used. As a stopping criterion, the maximum generation of 500 individuals was established. To improve the Pareto front, 20 optimization cycles (60 new samples) were required, reaching a final population of 100 individuals. It was found from the Pareto front that the values of the six variables providing the compromise solution, between Γ and Q, were H/D=1.572, L/D=1.518, h/D=0.565, w/D=0.361, d/D=0.108, and γ=92.141°. This solution reaches a Q of 0.00305 m3/s and a Γ of 1.699 m2/s. The results of this study were compared with the results reported by other authors, who optimized this type of turbine by applying the response surface methodology. The difference between these results was less than 9.61%.

Cooling of Heated Blocks with Triangular Guide Protrusions Simulating Printed Circuit Boards

There is no study that investigates triangular guide protrusions including their systematical geometrical changes together with the effects of channel height in the open literature in the context of the authors’ knowledge. Moreover, the number of laminar studies is less than turbulent studies, whereas low velocity or natural convection cases are still important, especially for small devices in small PCB passages. The objective of this study is to investigate numerically the effects of triangular guide protrusions for the enhancement of heat transfer from the blocks’ simulated electronic components in laminar flow conditions. Two-dimensional, incompressible, steady, and laminar flow analysis was performed to predict fluid flow and heat transfer characteristics for three heated blocks in a PCB (printed circuit board) passage with triangular guide protrusions mounted on the upper wall. The Galerkin finite element method of weighted residuals was used to discretize conservation equations. The effects of the channel expansion ratio and inlet velocity were investigated for five geometrical cases. If the size of the protrusions is increased, the existence of protrusions starts to affect the flow patterns on the lower wall. The size of the last protrusion controls the flow structure downstream of the last block. On the upper wall, after the last protrusion, a recirculation is formed and the length of the recirculation increases with an increasing Re number. Moreover, the reattachment length of recirculation after the last block increases with an increasing Reynolds number for a fixed expansion ratio. Expansion ratio and inflow conditions caused by blocks and protrusions have a great influence on the formation of secondary recirculation in addition to the Reynolds number. Heat transfer increases with increasing sizes of upper triangular protrusions. Maximum overall heat transfer enhancement is provided as 47.7% with the geometry of the maximum sized protrusions for the channel height of 3 h. In the case of 4 h, the maximum overall heat transfer enhancement is 24.21%. These enhancements in heat transfer that can be encountered in PCB cooling applications may help the PCB cooling designers.

Heat transfer enhancement in a square channel with a set of triangular prisms: an experimental study

ABSTRACT In this study, heat transfer behavior in a channel adapted with a set of equilateral triangular prisms was investigated experimentally in a turbulent flow regime, with a range of Reynolds numbers corresponding to 1x104<Re<8x104. The cross-section of the channel is square, and the triangular prisms were installed in the middle of the channel. In the test section of the channel, only the bottom wall was heated with constant heat flux. The square channel geometry and the triangular obstacle dimensions were assumed as fixed. Multiple equilateral triangular prisms were used with three different tandem arrangements and four different attack angles in the cross-flow of air. The heated wall temperatures, and channel inlet and outlet temperatures were measured using thermocouples on the test section. The triangular prisms changes flow structure in the flow field by cross-flow interaction, and increases the heat transfer from the heated surface. It was observed that compared to the smooth channel, the heat transfer was enhanced by about 22% for a single triangular prism. The obtained results are given as dimensionless parameters and discussed in this study. Results are compared with the existing literature and show strong similarities. Overall, in our study, triangular prisms showed a more noticeable increase in heat transfer for channel flows.

Numerical investigation of microchannel heat sinks with different inlets and outlets based on topology optimization

Topology optimization can generate better structures of microchannel with improved cooling performance. In this paper, microchannel heat sinks with five different inlet and outlet structure combinations are optimized using bi-objective topology optimization based on the density method. The layouts of channels are optimized to minimize the power dissipation and total heat generation at the same time. The results show that the straight line inlet and outlet with extension areas (SE) can reduce 20%-50% power dissipation when realizing the same heat transfer performance compared with traditional one channel inlet and one channel outlet (OC). Effects of Reynolds number, the ratio of solid and fluid thermal conductivity and the dimensionless heat generation coefficient in fluid domains are also investigated. The simple channels can be obtained with higher ratio of solid and fluid thermal conductivity and/or higher dimensionless heat generation coefficient in fluid domains. With optimization further considered in the inlet and outlet regions, better overall performance can be obtained. Finally, the 2D optimized structures are further validated by three-dimensional numerical simulation. It is found that the optimized design can realize 53.28% increment of Nusselt number with 40.89% reduction in pressure drop compared with traditional microchannel heat sinks.

Effects of secondary impinging on flow features and mixing performance in T-T jet reactors

The improvement of mixing performance for the micro/mini impinging jet reactor is a pivotal and attractive topic in the chemical industry. In the present study, the Planar Laser-Induced Fluorescence (PLIF) experiment and numerical simulation on a novel T-T jet reactor that generated secondary impinging were carried out. In the T-T jet reactor, the influence of secondary impinging on various flow regimes at diverse Reynolds numbers was investigated in detail. The results show that, compared with the classical T jet reactor, the mixing of different flow regimes is intensified by the secondary impinging. The number and shape of the impingement planes of the segregated flow and vortex flow are changed. The steady engulfment flow generates more fluid filaments under the secondary impinging. The agglomerate created by the vortex-merging of unsteady engulfment flow is strengthened and the flow topology of the unsteady symmetric flow is modified. All the above indicates that the mixing performance is improved. In addition, the impact of the T-T gap ratio (κ = l/w, where l and w are the width of the T-T gap and the inlet channel, respectively) on flow characteristics and mixing performance in the T-T jet reactor was also considered. The configuration with the lower T-T gap ratio, i.e., κ = 0.2, presented a better global mixing performance than those with the larger T-T gap ratios, i.e., κ = 0.6 and 1.0.

A Critical Analysis of Helical and Linear Channel Liquid Cooling Designs for Lithium-Ion Battery Packs

Thermal management systems are integral to electric and hybrid vehicle battery packs for maximising safety and performance since high and irregular battery temperatures can be detrimental to these criteria. Lithium-ion batteries are the most commonly used in the electric vehicle (EV) industry because of their high energy and power density and long life cycle. Liquid cooling provides superior performance with low power draw and high heat transfer coefficient. Two liquid cooling designs-the Linear Channel Design (LCD) and Helical Channel Design (HCD)-underwent multiple numerical and geometrical optimisations, where inlet mass flow rate, channel diameter, and inlet and outlet locations were analysed using CFD (computational fluid dynamics). The primary objectives were to maintain maximum temperatures and thermal uniformity within the operational limits derived from the literature. These were both achieved with the LCD using a mass flow rate of 7.50E-05 kgs−1. The Tmax goal was met for the HCD but not the thermal uniformity goal. The LCD achieved 1.796 K lower in maximum temperature and 8.740 K lower in temperature difference compared to the HCD, proving itself superior in both metrics. The HCD required a higher mass flow rate than the LCD to regulate temperatures, resulting in an undesirably high power consumption.

Modeling the hydrodynamics of a tidal inlet during bay-side storms

Bay-side storms, defined here as storms with tracks on the landward side of barrier islands, may disturb the hydrodynamics of inner bays to a larger extent than on the ocean side. These storms are common in large-scale O(>100,000 m) estuarine systems and have the potential to modify the circulation in bays and within tidal inlets. Here, we provide an overview of the hydrodynamic response of a tidal inlet under forcings caused by bay-side storms and explore the role of waves in modulating the release of storm surge from the back-barrier regions into the ocean. A two-dimensional horizontal numerical model including wave-current interactions is calibrated and validated against field observations of water levels and depth-averaged velocities at Oregon Inlet, NC. The model is then used to investigate the effect of synthetic bay-side storms with varying wave conditions and water levels based on those generated by Hurricane Irene (2011), which is the strongest bay-side storm to hit the Outer Banks of North Carolina in the last two decades. Effect of timing of the peak storm surge during the ebb and flood phases of the tide is also explored.Results from synthetic storms indicate that, during bay-side storms, the water level gradient along the inlet favors ebbing flows regardless of the timing of the storms relative to tidal phase. These results suggest that waves might be responsible for any influx of volume to the bay during high bay-side surge events. Wave blocking effects were found to be stronger along the ebb shoal and only reached the flood delta when bay water levels were nearly the same as the ocean water levels. Reduction of currents by waves in the inlet have the potential to extend the duration of the inundation period in the back barrier region. Bay-side storms also caused flux enhancement over inlet shoals and channels in the flood delta, which could have implications for circulation patterns as well as the morphodynamics of the system.

Direct assessment of giant red sea cucumber (Apostichopus californicus) sustainability through experimental fisheries

The giant red sea cucumber ( Apostichopus californicus) fishery in BC, Canada, is considered sustainable by managers but not by many harvesters. In 1997, the Kitasoo/Xai'xais First Nation began experimental fishing areas (EFAs) at Tolmie Channel and Laredo Inlet to test the effects of different exploitation rates on sea cucumber populations and determine what harvest levels are sustainable. These EFAs were annually surveyed by dive transects and subsequently harvested from 1998 to 2018. Bayesian surplus production models developed in 2011 indicated that the fishery was sustainable, after which the fishery changed from annual to 3-year rotational harvests. Here, we develop updated models to estimate the sustainability of the fishery using all currently available EFA data, including direct estimates of unfished biomass. Our models suggest that the fishery is likely to persist for 175 years at the current harvest rate annually or rotationally, though such long-term projections are likely inaccurate. We present methodology to generate scientific advice for the process of determining a maximum sustainable exploitation rate in the form of crash rate analysis.

Performance prediction for modified design of dew point evaporative cooler for air cooling

ABSTRACT Traditional air conditioning systems use lot of energy; thus, dew point evaporative air-cooling systems could be a good alternative. Many experts studied the impact of constructional and operating characteristics on Maisotsenko cycle (M-cycle) to improve its performance. Cooler performance is influenced by the heat exchanger. Heat exchangers were constructed using flat and corrugated plates. The present study proposes the use of geometrically modified trapezoidal corrugated plates for counter flow heat exchanger, which consists of alternate air and water flow passageways. The numerical model is developed to predict the performance under variety of inlet air conditions and channel dimensions. In the standard range of incoming air properties such as relative humidity, the performance parameters assist in making cooler recommendations. Comparison and validation of simulation results are done with published experimental data for corrugated and trapezoidal corrugated plate heat exchangers. For trapezoidal corrugated plates, simulation findings revealed 10% increase in wet bulb efficiency and 7% increase in dew point efficiency over corrugated plates. The efficiency of wet bulb and dew point decreases as channel gap widens. For trapezoidal corrugated plates, the larger channel spacing minimises pressure drop.

An Analysis of Energy and Internal Flow Characteristics of Open Inlet Channel Axial Flow Pumping Devices

For the purpose of studying the dynamic and inner flow features of an open inlet channel axial flow pump unit, in the present study, numerical calculations using the SST k-ω turbulence model are applied to an open inlet channel axial flow pumping unit based on the NS equation, and experimental validation is then performed. The experimental output indicates that the designed working conditions are Q = 350 L/s, head H = 5.065 m, efficiency η = 79.56%, and the maximum operating head is H = 9.027 m, which is about 1.78 times that of the design head; further, the pump device can operate in a wide range of working conditions. In addition, the design working conditions are within the range of high-efficiency operating conditions. The calculated values and the experimental comparison are all within a 5.0% margin of error; further, the numerical calculations are reliable. The hydraulic loss of the inlet channel under the design condition Q = 350 L/s is 0.0676 m, which satisfies the relationship of the quadratic function. The uniformity of the impeller inlet velocity is 80.675%, and the weighted average angle of the velocity is 79.223°. The hydraulic loss of the outlet channel under the design condition Q = 350 L/s is 0.3183 m, and the hydraulic loss curve is a parabola with an upward opening. The flow state of the pump device is sensitive to changes in the working conditions; additionally, the flow state is optimal under the design working conditions. In this study, the energy and inner flow features of the open inlet axial flow pumping units are revealed, and the research outcomes can be used as a reference for the design and operation of similar pumping units.

Heat dissipation performance of hybrid lithium battery thermal management system using bionic nephrolepis micro-channel

To enhance heat dissipation performance at high-rate discharge conditions, a thermal management system with bionic water-cooling/composite phase change material is nominated for 26,650 lithium-ion cell, which is inspired by the growth mode of the Nephrolepis. The effects of the external diameter, layer number of bionic micro-channel, liquid flow tempo, and the arrangement of the channel on the highest temperature and temperature differences of the cell at a discharge rate of 4C are investigated through simulated and physical experiments. Furthermore, the thermal performance of the battery thermal management system for battery module are analyzed at different inlet flow tempos at 4C and 5C discharge rates. The result indicates that the highest temperature and temperature difference of the cell decrease with the increase of the layer number and external diameter of the micro-channel at a constant channel inlet flow tempo and projected angle of the micro-channel. Under the conditions of the ambient temperature of 303.15 K and the mass fraction of composite phase change material is about 40 %, the highest temperatures can be regulated at 310.28 K and 309.99 K, and the temperature differences among cells are 4.06 K and 4.21 K at a discharge ratio of 4C and 5C, respectively.

A Model for Sound Propagation Through Corrugated Porous Structures With Mean Flow

Abstract For applications of porous materials where mean pressure drop is a concern, packaging the material into a corrugated structure is better compared to other geometries such as block or wedge shapes. The goal of this study is to integrate noise reduction functionality within that material, which requires an understanding of sound propagation through corrugated porous structures, including flow effects. The corrugated porous structure involves porous partitions separating inlet and outlet fluid channels. The porous materials considered are periodic octet-truss and body-centered cubic unit cells, and sound propagation across these porous partitions is modeled using the Johnson–Champoux–Allard model. The predicted transmission loss (TL) is benchmarked using designed additively manufactured corrugated structures measured using a flow duct. The laminar flow regime is maintained across the porous structure to reduce flow-noise effects. It is shown that the TL for a given corrugated structure increases with a decrease in porosity, and the impact of flow becomes significant as the porosity decreases. The influence of flow on TL also depends on the unit cell configuration. Furthermore, the model provides insights into pressure and acoustic particle velocity distributions within the corrugated structure and reveals regions of the porous material that effectively participate in noise reduction.

Investigation of Flow-Induced Noise Characteristics in the Oblique Flow Pump

An oblique flow pump is widely used in farmland irrigation and drainage, water transfer projects, thermal power generation, and other fields. However, unstable flow factors in the oblique flow pump easily lead to pump vibration and noise. To improve the stability of pump operation and optimize the operating environment, it is necessary to study the flow-induced noise characteristics of oblique flow pumps. In this paper, CFD and noise simulation software are used to calculate the flow field and sound field of the oblique flow pump. The internal flow characteristics and flow-induced noise characteristics of the oblique flow pump were studied. The results show that when the flow rate of the oblique flow pump deviates from the optimal operating point, especially in the small flow rate, due to the phenomena of backflow and flow separation, more high-energy vortices are produced in the flow channel, and the vortices are distributed in a wide area, which will cause greater flow-induced noise. It is found that with the increase in flow rate, the sound pressure level of flow noise in the inlet channel gradually decreases, the sound pressure level in the guide vane region first decreases and then increases, and the sound pressure level is the lowest at 1.0Q. Generally speaking, the noise sound pressure level in the outlet channel region of the pump also gradually decreases. In addition, at the blade frequency, the radiated noise of the oblique flow pump can show dipole characteristics under various flow conditions, and the radiation level of sound pressure increases with the increase in flow rate. This paper can provide a theoretical basis for the mechanism research and control strategy of flow-induced noise in oblique flow pumps.

Simulation and optimization of thermal performance in diverging/converging manifold microchannel heat sink

Increasing complexity of electronic devices and chips places increasingly stringent requirements on heat sinks. A novel manifold microchannel heat sink with diverging/converging channels is proposed to improve heat transfer performance. The flow and heat transfer characteristics under single-phase are investigated numerically. The effects of two key parameters, manifold inlet to outlet ratio α and channel inlet to outlet ratio β, and their combinations on the thermal-hydraulic performance are explored. The results show that, in the single parameter optimization, a moderately diverging manifold layout and a converging channel layout each have the best enhancement effect on heat transfer for given pumping power, reducing the thermal resistance by 11.1% and 13.5% than homogeneous structure, respectively. When both parameters are set as optimization variables, the parameter combinations with enhanced performance are distributed in a sloping downward band in the parameter diagram. The configuration with α = 1/9 and β = 9 has the best reinforcement effect, reducing the thermal resistance by 19.18% for a given pumping power of 5×10−4 W. In addition, the heat transfer characteristics of the optimum and original configurations under non-uniform heating flux are also investigated for application, with the optimum configuration showing better performance at both temperature level and temperature uniformity.