L-shaped Cavity Research Articles

Compact mid-infrared dual-wavelength optical parametric oscillator pumped by Yb-doped fiber lasers based on two PPMgLN crystals

A compact mid-infrared (MIR) dual-wavelength optical parametric oscillator (OPO) pumped by Yb-doped fiber lasers (YDFLs) based on dual-crystal with an L-shaped cavity structure is demonstrated. Two periodically poled MgO-doped lithium niobite (PPMgLN) crystals with polarization periods of 30.44 μm and 28.96 μm are pumped by two YDFLs, respectively. The dual-wavelength output at 3.45 μm and 4.00 μm is obtained synchronously by adjusting the double pump power. When the total power of double-end pumping is 28.98 W with a ratio of 2:3, the pulse width is 60.80 ns under the repetition frequency of 110 kHz, the output power is 1.483 W@3.45 μm and 1.703 W@4.00 μm, respectively. The total conversion efficiency is 10.99%. By utilizing this cavity structure, the gain and wavelength tuning of the two OPOs can be controlled separately. Meanwhile, the pulse width is 46.93 ns@3.45 μm and 39.38 ns@4.00 μm, respectively. The laser beam quality closely approaches the theoretical quality of the fundamental mode beam. Additionally, by independently adjusting the temperature of the two PPMgLN crystals from 20 °C to 150 °C, tunable mid-infrared laser outputs with wavelengths of 3.448–3.272 μm and 4.006–3.864 μm are achieved. The corresponding tuning bandwidths are 176 nm and 142 nm, respectively.

Vibroacoustic Analysis of Laminated Composite L-shaped Acoustic Cavity using Multi-domain Coupled BE-FE Method

Vibroacoustic Analysis of Laminated Composite L-shaped Acoustic Cavity using Multi-domain Coupled BE-FE Method

Multipactor analysis of 431 MHz L-shaped inductive output tube cavity

Gridless inductive output tubes (IOTs) offer compact size and high-power amplification at sub-GHz frequencies. Minimizing cavity dimensions in the interest of compactness leads to smaller gaps, which may cause multipactor discharge under high-power operating conditions. The uncontrolled electron growth resulting from multipactor breakdown can lead to undesired effects including surface damage and system failure. This paper performs a parallel-plate multipactor analysis for a high-Q, L-shaped, aluminum, 431 MHz cavity designed for a gridless IOT to be operated in the MW-power regime. The cavity gap is 27 mm, and diameter is 339 mm. Multipactor susceptibility regions are calculated for non-zero emission energy, half-cycle, and non-half-cycle multipactor using a semi-analytic approach and a standard aluminum secondary electron yield (SEY) curve. The analytical results are validated with particle-in-cell simulation in CST Studio. Simulation results show a voltage range of 6.4–19 kV, compared to the analytically calculated values of 8.2 and 18.3 kV for the lower and upper bounds, respectively. Fluorocarbon coating as a means to reduce secondary electron emission is simulated, which shows 46% reduction in peak particle population with an 11.2 nm PTFE coating, with further reduction as coating thickness increases. The results show that the L-shaped cavity is a suitable choice for this IOT design as it does not exhibit single-surface multipactor and will not develop two-surface multipactor at full-power operation.

Double-Diffusive Natural Convection in L-Shaped Cavity by Lattice Boltzmann Method: Numerical Study

The double diffusive natural convection is studied numerically on an L-shaped cavity using lattice Boltzmann method (LBM). The top and right side of the cavity is insulated, the left and the bottom side of the cavity are maintained at high temperature, and remaining sides are considered as cold wall. This study is carried out using a two-dimensional nine-directional (D2Q9) lattice structure. Single relaxation time model is adopted to solve the LBM equations. The effects of different Rayleigh numbers (Ra = 103–105), aspect ratio (0.2–0.8), Prandtl number (Pr = 0.054, 0.7, 6.2, and 50), Lewis number (2), and buoyancy ratio (−2) on the temperature, concentration, and streamline contours are presented. For the selected range of operating parameters in this study, the heat and mass transfer are more pronounced for horizontal wall than vertical. At low Pr, the difference between horizontal wall to vertical wall average Nusselt number (Nu) is 11.2% and when Pr = 50, the same difference in average Nu is 37.5%. Similarly, the average Sherwood number between horizontal and vertical wall differences are 19.5% and 31.7%. For Ra = 105, the convection rate reduced by 46% and mass diffusion reduced by 52% between Pr = 0.054–50.

Study of High-Power Gridless Inductive Output Tube With L-Shaped Cavity

Study of High-Power Gridless Inductive Output Tube With L-Shaped Cavity

Adjoined ISPH method and artificial intelligence for thermal radiation on double diffusion inside a porous L-shaped cavity with fins

PurposeThe purpose of this study is to adapt the incompressible smoothed particle hydrodynamics (ISPH) method with artificial intelligence to manage the physical problem of double diffusion inside a porous L-shaped cavity including two fins.Design/methodology/approachThe ISPH method solves the nondimensional governing equations of a physical model. The ISPH simulations are attained at different Frank–Kamenetskii number, Darcy number, coupled Soret/Dufour numbers, coupled Cattaneo–Christov heat/mass fluxes, thermal radiation parameter and nanoparticle parameter. An artificial neural network (ANN) is developed using a total of 243 data sets. The data set is optimized as 171 of the data sets were used for training the model, 36 for validation and 36 for the testing phase. The network model was trained using the Levenberg–Marquardt training algorithm.FindingsThe resulting simulations show how thermal radiation declines the temperature distribution and changes the contour of a heat capacity ratio. The temperature distribution is improved, and the velocity field is decreased by 36.77% when the coupled heat Cattaneo–Christov heat/mass fluxes are increased from 0 to 0.8. The temperature distribution is supported, and the concentration distribution is declined by an increase in Soret–Dufour numbers. A rise in Soret–Dufour numbers corresponds to a decreasing velocity field. The Frank–Kamenetskii number is useful for enhancing the velocity field and temperature distribution. A reduction in Darcy number causes a high porous struggle, which reduces nanofluid velocity and improves temperature and concentration distribution. An increase in nanoparticle concentration causes a high fluid suspension viscosity, which reduces the suspension’s velocity. With the help of the ANN, the obtained model accurately predicts the values of the Nusselt and Sherwood numbers.Originality/valueA novel integration between the ISPH method and the ANN is adapted to handle the heat and mass transfer within a new L-shaped geometry with fins in the presence of several physical effects.

Numerical investigation of mixed convection inside a three-dimensional l-shaped cavity filled with hybrid-nanofluids in the presence of a heating block

Numerical investigation of mixed convection inside a three-dimensional l-shaped cavity filled with hybrid-nanofluids in the presence of a heating block

Multimode vibrational strong coupling in direct laser written mid-IR plasmonic MIM nano-patch antennas

Strong coupling of mid-infrared (mid-IR) vibrational transitions to optical cavities provides a means to modify and control a material’s chemical reactivity and offers a foundation for novel chemical detection technology. Currently, the relatively large volumes of the mid-IR photonic cavities and weak oscillator strengths of vibrational transitions restrict vibrational strong coupling (VSC) studies and devices to large ensembles of molecules, thus representing a potential limitation of this nascent field. Here, we experimentally and theoretically investigate the mid-IR optical properties of 3D-printed multimode metal–insulator–metal (MIM) plasmonic nanoscale cavities for enabling strong light–matter interactions at a deep subwavelength regime. We observe strong vibration-plasmon coupling between the two dipolar modes of the L-shaped cavity and the carbonyl stretch vibrational transition of the polymer dielectric. The cavity mode volume is half the size of a typical square-shaped MIM geometry, thus enabling a reduction in the number of vibrational oscillators to achieve strong coupling. The resulting three polariton modes are well described by a fully coupled multimode oscillator model where all coupling potentials are non-zero. The 3D printing technique of the cavities is a highly accessible and versatile means of printing arbitrarily shaped submicron-sized mid-IR plasmonic cavities capable of producing strong light–matter interactions for a variety of photonic or photochemical applications. Specifically, similar MIM structures fabricated with nanoscopic voids within the insulator region could constitute a promising microfluidic plasmonic cavity device platform for applications in chemical sensing or photochemistry.

Solution of MHD-stokes flow in an L-shaped cavity with a local RBF-supported finite difference

One of the popular meshless methods for solving governing equations in applied sciences is a local radial basis function-finite difference (RBF-FD). In this paper, we proposed a new idea for an L- shaped (or like T- and Z-shaped) domain based on the domain decomposition. RBF-FD formulation is used at the interface points to get a better solution, while the classical FD is applied to all sub-regions. We use the algorithm based on the Gaussian-RBF (RBF-GA) in the stable calculation of the weights to avoid choosing optimal shape parameters. Stencil size is considered the nearest n-points (9,12,15) and benchmark results are presented for divided-lid driven cavity. Further, Navier–Stokes equations adding the Lorentz force term with Stokes approximation for a single-lid L-shaped cavity exposed to inclined magnetic field are solved by the devised numerical method. The flow structure is analyzed in aspect of streamline topology under the various magnetic field rotation (0∘≤α≤90∘ ) and its strength (M=10,30,50,100 ).

Fluid Structure Interaction Analysis of Natural Convective Flow and Heat Transfer in an L-Shaped Cavity

The primary objective of this research work is to perform a numerical study on the fluid-structure interaction (FSI) of flow and heat transfer characteristics within an L-shaped cavity. The investigation will focus on analyzing the effects of various key variables, namely the Rayleigh number and wall elasticity, on the observed results. To accomplish this, the COMSOL software, which utilizes the finite element method, will be employed as the numerical simulation tool. To ensure the reliability and credibility of the obtained results, the findings of this research were rigorously validated against previously published data available in the literature. The outcomes of this investigation were presented using various visualization techniques. Streamlines, temperature contours, and heat transfer enhancement will be among the visual representations used to illustrate the flow and temperature distribution within the L-shaped cavity. Anticipated results indicated that the calculations of the average Nusselt number exhibited a strong dependency on the Rayleigh number and the wall elasticity. As such, the average Nusselt number was higher for flexible wall compared to rigid wall model. Moreover, the average Nusselt number was found to increase with an increase in Rayleigh number. Young’s modulus was found to have a profound effect on the patterns of the streamlines. The average Nusselt number was found to decrease with an increase in the Young’s modulus. This study may provide valuable insights into optimizing heat transfer and designing efficient thermal management systems for various practical applications.

Second Law Analysis for Free Convection in an L-Shaped Cavity Filled with Nanofluid

The paper aims to analyze the effects of various Prandtl number and different nanoparticles for heat transfer and entropy generation of free convection laminar fluid flow in an L-shaped cavity filled by nanofluid. To investigate the second law characteristics of free convective flow and heat transfer from an L- shaped geometry filled by water and nanofluids (Cu-water, Ag-water, Al2O3-water), the effects of Prandtl number and various nanoparticles on the average Nusselt number, total entropy generation and Bejan number has been numerically analyzed. Isotherms, stream function and entropy generation caused by heat transfer are also presented for various Prandtl numbers and various nanoparticles. The governing equations are solved using penalty finite element method with Galerkins weighted residual technique. The results reveal that Ag-water nanofluid with highest Prandtl number gives the highest amount of irreversibility as well as rate of heat transfer. Cu-water and Ag-water nanofluid produces more irreversibilities than Al2O3-water nanofluid and base fluid. Also the results show that the Nusselt number and Bejan number increase with the increase of Prandtl number. Therefore, Prandtl number may be an important parameter for desired heat transfer increment with decreasing entropy generation in the given geometry.

A decoupled finite element scheme for simulating the dynamics of red blood cells in an L-shaped cavity

A decoupled finite element scheme for simulating the dynamics of red blood cells in an L-shaped cavity

Natural ventilation system with thin microperforated panel (MPP) component for wideband sound insulation

Natural ventilation system plays a pivotal role in building sustainability. However, the design is challenging due to the conflict between opening area requirements and sound insulation capability. Here, we design and experimentally demonstrated such a system with attenuation and bandwidth enhancement. For this, we use MPP components in L-shaped cavity that can be tuned at the targeted frequency range individually, while its overall thickness is reduced due to the benefit of the L-shape that forms a coiled backing air cavity. Moreover, adopting the MPP components allow the system to be easily tuned at various frequency regimes under fixed thickness, particularly at a low frequency that might be difficult for the porous liner cases. It is found that sound insulation bandwidth of 1000 Hz and more can be produced by such a system where the transmission loss of 20 dB and above are pronounced. Most of the features in the theoretical calculation are also found in the experimental results for the same structures. The results are promising for green building applications where sound insulation and air circulation need to be present simultaneously from the natural ventilation system.

The Impact of Cavities in Different Thermal Applications of Nanofluids: A Review

Nanofluids and nanotechnology are very important in enhancing heat transfer due to the thermal conductivity of their nanoparticles, which play a vital role in heat transfer applications. Researchers have used cavities filled with nanofluids for two decades to increase the heat-transfer rate. This review also highlights a variety of theoretical and experimentally measured cavities by exploring the following parameters: the significance of cavities in nanofluids, the effects of nanoparticle concentration and nanoparticle material, the influence of the inclination angle of cavities, heater and cooler effects, and magnetic field effects in cavities. The different shapes of the cavities have several advantages in multiple applications, e.g., L-shaped cavities used in the cooling systems of nuclear and chemical reactors and electronic components. Open cavities such as ellipsoidal, triangular, trapezoidal, and hexagonal are applied in electronic equipment cooling, building heating and cooling, and automotive applications. Appropriate cavity design conserves energy and produces attractive heat-transfer rates. Circular microchannel heat exchangers perform best. Despite the high performance of circular cavities in micro heat exchangers, square cavities have more applications. The use of nanofluids has been found to improve thermal performance in all the cavities studied. According to the experimental data, nanofluid use has been proven to be a dependable solution for enhancing thermal efficiency. To improve performance, it is suggested that research focus on different shapes of nanoparticles less than 10 nm with the same design of the cavities in microchannel heat exchangers and solar collectors.

NATURAL CONVECTION FLOW AND HEAT TRANSFER IN AN L-SHAPED CAVITY PARTIALLY FILLED WITH POROUS MEDIUM: NUMERICAL ANALYSIS

In an L-shaped cavity partially filled with a porous material, natural convection flow and heat transfer are quantitatively investigated. The effect of numerous significant parameters on isotherms, streamlines, and heat transport characteristics is investigated within the enclosure. The Rayleigh number, Darcy number, effective heat conductivity of the porous medium, aspect ratio, and thickness of the porous layer are all investigated. The governing equations are solved using the Galerkin technique with weighted residuals. The findings of this study demonstrate that an L-shaped cavity exhibits fascinating properties. As a result, as the aspect ratio of the L-shaped cavity increases, the average Nusselt number decreases. Furthermore, raising the Rayleigh number, as well as the effective thermal conductivity of porous media, improved the average Nusselt number. In the case of natural convection, the thickness of the porous layer is shown to be inconsequential.

Numerical analysis of unsteady mixed convection heat transfer characteristics of nanofluids confined within a porous lid-driven L-shaped cavity

The numerical analysis of unsteady combined convective heat transfer properties of kerosene-alumina nanofluid restricted in an L-shaped porous lid-driven cavity has been examined in this research. Fluid flow governing equations and conjugate heat transport along with the corresponding boundary conditions are used to express the physical problem mathematically. Firstly, boundary conditions and governing equations are transformed into non-dimensional forms using a series of appropriate transformations. Later on, the transformed non-dimensional equations are solved by utilizing the Finite Element Method based on the Galerkin residuals. A comparison with earlier available work is shown and turned out to be a great agreement. Numerical solutions are acquired in a wide variety of governing variables. The governing variables in this study are the Darcy number ( Da ), Reynolds number ( Re ), Richardson number ( Ri ), solid volume fraction (δ), time parameter (τ), etc. The numerical findings of flow and thermal fields are represented graphically in respect of isotherms, streamlines, and average Nusselt number at the hot surface of the cavity. The Re and Da are found to have an extensive impact on the isotherms and streamlines in the cavity, and also in determining the average heat transmission rate.

MHD hybrid nanofluid convection and phase change process in an L-shaped vented cavity equipped with an inner rotating cylinder and PCM-packed bed system

In this study, convective heat transfer and phase change process are analyzed for an L-shaped vented cavity equipped with an inner rotating cylinder and phase change material-packed bed (PCM-PB) system under magnetic field during hybrid nanofluid convection. The numerical work is performed for different values of Reynolds number (Re between 200–1000), rotational Reynolds number (Rew between −1000–1000), size of the cylinder (R between 0.05H-0.15H) and Hartmann number (Ha between 0–40) while hybrid Ag/MgO nanoparticle loading amount in water is 2%. It is observed that the vortex size and their distributions in the cavity and within the PCM-PB system can be controlled by varying rotating cylinder size and rotational speed along with the magnetic field. With higher cylinder size, phase change becomes fast while complete phase transition time (tP) is reduced by about 22% and average Nusselt number (Nu) rises by about 86% at Rew = −1000. Rotational direction of the cylinder is effective for phase transition dynamics while at Rew = −1000, tP rises up to 27% when compared to non-rotating cylinder case. Magnetic field strength is a good parameter for vortex suppression. At the highest strength, phase change becomes fast and average Nu rises up to 26.5% at Rew = −1000. ANFIS based modeling approach is used for impacts of rotating cylinder on the phase change dynamics in the L-shaped vented cavity.

CW and Q-switched operations of a Tm3+:YAP laser at 1892–1994 nm In-band fiber-laser pumped at 1670 nm

Tm3+:YAP lasers in-band fiber-laser pumped at 1670 nm with a linear or L-shaped cavity were studied in CW, actively and passively Q-switched regimes. High-efficiency CW and repetitively-pulsed operations were registered at three spectral regions: 1987–1994 nm, 1935–1941 nm and 1892–1897 nm. The transition between these three spectral regions was achieved by controlling the pump power and the output mirror in a laser cavity. The highest CW output power that was achieved without degrading the beam quality was 12.2 W at the 52% slope efficiency with respect to the incident pump. Acousto-optically Q-switched operation with the average power of 9.8 W at the 20 kHz pulse repetition rate (PRR) and 6 W at 3 kHz PRR was achieved, the pulse energy was scaled up to 2.7 mJ at 0.5 kHz PRR. The passive Q-switch operation at 1935–1938 nm was obtained using a Cr2+:ZnSe saturable absorber; the pulse energy reached 150 µJ at the 20 kHz PRR

Hydrothermal behavior of micro-polar Nano-Encapsulated phase change materials (NEPCMs) in an inclined L-shaped cavity

This paper investigates natural convection and entropy generation of the Nano-Encapsulated phase change materials (NEPCMs) in an inclined L-shaped cavity. The NEPCMs are made up of core and shell in which the PCMs are the core section that are capsulated in Nano-shells. These NEPCM particles go through phase change from solid to the liquid while absorbing the heat and release it when their phase changes back to solid. The Navier-Stokes equations are solved by Finite Element Method (FEM) to simulate the behavior of NEPCMs under a set of defined boundary conditions. The effect of Rayleigh number (10 4 -10 6 ), micro-rotation parameter (0–2), Nano particle's concentration (0.01–0.05), Stefan number (0.1–0.5), and non-dimensional fusion temperature (0.1–0.3) on the Nusselt number and entropy generation of the fluid flow is also analyzed. The results reveal that the Stefan number, micro-rotation parameter, and non-dimensional fusion temperature have a negative impact on NC heat transfer of NEPCMs and reduce the Nu avg up to 25%, 42%, and 15% respectively. Conversely, the nanoparticle concentration enhances the Nu avg up to 36%.

Shape effects of TEG mounted ventilated cavities with alumina-water nanofluids on the performance features by using artificial neural networks

Shape effects of TEG mounted vented cavities on the performance characteristic during alumina-water nanofluid convection are numerically assessed by using finite element method. Rectangular, triangular, l-shaped and Ushaped cavities are used. The interface temperatures of hot and cold side are varied by changing the cavity shape, opening ratio (OR) and Reynolds number (Re). The highest hot side temperature is obtained with l-shaped cavity followed by U, T and R-shaped cavities. When using T, L and U shaped cavities, the rise of the power are calculated as 38%, 78% and 76% atRe=1000 when compered to rectangular cavity. The power rises with higher OR while increment amounts are 83.9%, 63.5%, 42% and 87.8% for R, T, L and U cavities a Re=1000. When nanofluid is used at the highest loading, 11%, 10.3%, 9% and 8.5% rise of power are achieved for R, T, L and U shaped cavities while the amount is than 5% when different sizes of particles are considered. Neural network modeling with 10 neurons in the hidden layer provides accurate power outputs for all shaped cavities.