Unsteady Computational Fluid Dynamics Research Articles

Experimental and numerical validation of a Francis turbine draft tube designed for mitigation of pressure fluctuations

This paper presents an experimental and numerical investigation of the internal flow in a Francis turbine draft tube previously designed for minimizing pressure fluctuations and energy losses in off-design conditions. The design of the draft tube geometry is based on an original approach combining Design of Experiments and steady/unsteady Computational Fluid Dynamics (CFD) simulations of the draft tube internal flow. The proposed method provides new insight on the influence of the draft tube geometry on the flow dynamic behaviour on one hand and enables the determination of a geometry promoting flow stability and hydraulic performance on another hand. CFD simulations of the internal flow in the final geometry showed promising results in terms of flow stability compared with the initial geometry designed by conventional CFD-aided methods. A reduced-scale model of the prototype machine featuring the final draft tube geometry is finally installed and tested in laboratory. Tests include performance and pressure fluctuations measurements over the complete operating range. The analysis of the results shows that the draft tube flow remains globally stable over the complete part-load range with pressure fluctuations amplitude lower than 1% of the net head. It is also shown that the dominant pressure component at the runner outlet in the draft tube cone is of synchronous nature. The physical mechanisms of excitation are finally highlighted by analysis of unsteady CFD simulation results.

Eigenfrequencies of rotating discs in dense fluid: imposed modal motion approach

The mode split on disc like structures rotating in a dense fluid leads to a deviation of eigenfrequencies at high rotational speeds compared to their values in still water. Predicting eigenfrequencies correctly is essential to avoid fatigue cracks on prototype turbine runners. Analytical models for simple geometric configurations and complex numerical models using fully coupled fluid structure interaction to predict the mode split on arbitrary geometries exist. We are presenting a complementary approach of intermediate complexity applicable to arbitrary geometries. Mode shapes and modal parameters are computed by finite element analysis in still water. These mode shapes are imposed with a harmonic variation in time during an unsteady computational fluid dynamics computation. From the interaction between the flow and the modal motion, the modal force and the modal work can be computed. These can be converted into added modal mass and hydrodynamic damping and further into the shift of the eigenfrequency under rotation due to the fluid for a given mode. The tendencies of the frequencies with rotation compare reasonably well with experimental data. The numerical method can be applied to disc rotation speeds far beyond the range of experimental data revealing interesting tendencies and a phenomenological interpretation of the cause of the mode split.

Remarkable dynamic adsorption of Hg2+ ions on the magnetic MOF nanocomposite (CuNi-BTC@Fe3O4): Experimental and modeling using GA+CFD+ANFIS method

The magnetic bimetallic metal-organic framework (MOF) nanocomposite was fabricated using the facile preparation method for the removal of mercury ions in the fixed bed column. The several analyses including XRD, TEM, BET and VSM were also carried out to characterize the physico-chemical properties of the synthesized sample (CuNi-BTC@Fe3O4). The Langmuir model with a maximum adsorption capacity of 144.32 mg/g was fitted well with equilibrium data. The performance of the adsorption column was evaluated under the various operating conditions including length of bed (10, 15, 20 cm), flow rate of feed (10, 15, 20 ml/min) and initial concentration of mercury ions in the inlet (25, 50, 75 mg/l). The breakthrough time was measured to be about 581.1 min at the proper operating conditions including 15 cm of bed height, 50 mg/l of feed concentration and 10 ml/min of feed flow rate. The commercial models including Thomas and Yoon-Nelson were investigated for the determination of the adsorption behavior of Hg (II) in the adsorption column. The results indicated the good agreement between the experimental data and Yoon-Nelson model (R2 > 0.99). The combination model consisting of the unsteady computational fluid dynamics (CFD), an adaptive neuro-fuzzy inference (ANFIS) and genetic algorithm (GA) was developed to simulate the uptake of Hg (II) ions in dynamic bed. The employed ANFIS was also coded by using five layers to predict the source term of mass transfer equation as the most significant parameter of the modeling which must be calculated with high precision. The generated Gaussian membership functions i n the ANFIS model was optimized by applying GA. Finally, the CFD (the first order implicit) was linked with ANFIS to describe the dynasmic adsorption of mercury ions. The validation illustrated a good matching between the experimental data and the output of the combination model (R2 > 0.999).

Dynamics of a microsphere inside a spherical cavity with Newtonian fluid subjected to periodic contractions

Mechanical forces on the nucleus of a biological cell can play a significant role in its positioning within the cell. Some models for the migration of the nucleus are based on biochemical signals, which have a very slow response, and others on the mechanical actions of direct pushing–pulling forces, relying on the cytoskeleton and cell contractility. In the present work, hydrodynamic drag forces, produced by the surrounding membrane movement and acting on a spherical model of the nucleus, are numerically investigated. The space distributions of force and drag resistance are estimated by unsteady three-dimensional computational fluid dynamics simulations. These distributions are functions of sphere size and position, and they are fitted to mathematical models. Dynamic simulations are performed using these mathematical models to compute the trajectory of the microsphere under the action of thousands of position-dependent pushing–pulling forces. A characteristic time is estimated by linearization of the equation, and a dynamic simulation is performed with one-dimensional finite differences. With this approach, it takes a few minutes to simulate several hours of nuclear migration. It is shown that in the long term, nuclei tend to migrate to the center of the cell, especially when it is small compared with the cell size. The model presented here, based exclusively on hydrodynamic interaction in a Newtonian fluid, shows that pushing–pulling forces on the nucleus, produced by periodic contractions of the cell membrane, will cause it to migrate to the center of the cell in a manner that is in agreement with experimental observations.

Unsteady Simulation of the Internal Flow in a Tubular Pump Considering Tip-Leakage Flow

Tip-leakage vortex is a commonly-seen phenomenon in tubular pump runners because there will be always gap between blade and pump shroud. In the operation process, the tip-leakage vortex is unstably varying. Pressure in the vortex core is relatively low and may induce cavitation in extreme conditions. The operation stability will be strongly impacted. As an effective tool, computational fluid dynamics (CFD) can be used in predicting the vortical flow in pumps. In this study, unsteady CFD simulation is conducted with the visualization of tip-leakage vortex using the Q criterion. The design-load condition is mainly studied. The temporal characters, their frequency domain features and their spatial distributions are fully analysed. This study will help understanding the tip-leakage vortical flow in the tubular pump and enhance the operation stability of low-head pumping stations.

Buffet boundary prediction using RANS-based criteria and adjoint methods

In this work a procedure is proposed for a fast estimate of the transonic buffet boundary on aerofoils and wings. This algorithm aims to be an alternative to unsteady computational fluid dynamics simulations that are prohibitively expensive for complex flow cases. The algorithm combines steady Reynolds-averaged Navier-Stokes simulations with an adjoint method. Reynolds-averaged Navier-Stokes simulations were used to determine the buffet onset by means of suitable criteria, while the adjoint method was used to compute the sensitivities of the buffet parameters to the flight conditions, and draw the buffet boundary. The procedure was tested for two-dimensional configurations with available experimental data and for two different criteria. Particular attention was paid to the efficiency of the method and its ability to reduce computational cost with respect to purely RANS criteria for buffet boundary estimation. Possible variations to the procedure were also discussed in the results section together with the effect of some key parameters of the proposed algorithm.

Power enhancement CFD based study of Darius wind turbine via roof corner placement

In this paper, the concept of positioning micro-scale wind turbines on the roof of buildings is being studied for a Darrieus wind turbine, located above the roof of a cubic building at two different positions and operating under different wind flow conditions. The turbine has a height of 2 m and is positioned at 1 or 2 m from the top of the roof of a 30.5 m cubic building. The simulation methodology based on 3D unsteady computational fluid dynamics is first presented, including mesh details and experimental validation of the unperturbed flow baseline configuration. The simulation of different configurations shows that the turbine's Coefficient of Power can reach 0.55 by positioning it above the side corners of the building when the wind reaches the building at 45°. This position indicates that the synergy between the building and the turbine is quite strong such that the turbine should be placed not on top of the frontal corner but on top of one of the side corners. The power produced by this turbine at this location is 464 W. This placement leads to a significant increase in comparison with the maximum coefficient of power (Cp) of 0.32 (equivalent to a power of 378 W) when the turbine does not interact with a building. This increase in performance is very impressive. An increase of 25% in the power extracted can lead to better integration of wind turbines on roofs.

A numerical performance analysis of a ducted, high-solidity tidal turbine in yawed flow conditions

Analysing the fluid dynamic performance of a bare rotor when succumb to yawed flow conditions has consistently presented a diminishment in mechanical power conversion efficacy. Introducing a duct along the rotor perimeter has been acknowledged to sustain performance, yet the causation behind this phenomenon is uncertain. This study puts forward an investigation into the hydrodynamic performance concerning a true-scale, ducted, high-solidity tidal turbine in yawed free-stream flows by utilising blade-resolved, unsteady computational fluid dynamics. Investigating the performance within an angular bearing range of 0o to 45o with the turbine axis, increases in mechanical rotational power and thrust are acknowledged within a limited range at distinct tip-speed ratio values. Through the multiple yaw iterations, the maximum attainment falls at an angle of 23.2o, resulting in a power increase of 3.44% to a peak power coefficient of 0.35 at a nominal tip-speed ratio of 2.00, together with an extension of power development along higher tip-speed ratios. In verification of the power increase, the outcomes are analysed by means of linear momentum theory; by utilising area-averaged values of static pressure acquired from annular radial surfaces fore and aft of the rotor, an analogous relationship with the blade-integrated outcomes is attained. The analysis concludes that, at higher tip-speed ratios, the pressure drop across the rotor increases at limited flow bearings, enhancing the resultant axial force loading upon the blades, hence providing further performance augmentation of the ducted, high-solidity tidal turbine.

Determination of efficient configurations of vertical axis wind turbine using design of experiments

This study aims to optimize the design parameters of a vertical axis wind turbine using design of experiments (DOE). Response surface methodology combined with desirability optimization was used to optimize multiple parameters such as the chord length, number of blades, aspect ratio, and pitch angle. The range of contributing parameters was selected using one factor at a time (OFAT) approach, and the performance parameters were evaluated by applying the double multiple streamtube theory. Datasets retrieved from the Q-Blade open-source software were employed in the DOE to determine the optimal configurations. Based on response surface investigation, a quadratic model was established and the accuracy of the model was determined by applying analysis of variance, goodness of fit, normal plot of residuals, and R-squared values. The optimized chord length, number of blades, pitch angle, and aspect ratio were 0.546 m, 03, −2.82°, and 0.808, respectively. The maximum power coefficient of 0.45 was obtained at a tip speed ratio of 3 from the optimized design parameters. The analysis revealed an increase of approximately 8.43% in the maximum power coefficient of the proposed wind turbine. A 3D unsteady computational fluid dynamics model along with Reynolds-Averaged Navier-Stokes equations were utilized to verify the obtained results, and a maximum difference of less than 1.5% was found. A standard H-rotor Darrieus configuration obtained from the OFAT approach was also tested at different wind speeds for comparison. The analysis revealed that when the wind speed was less than 3.85 m/sec, the standard Darrieus produced no power; however, the self-starting speed of the optimized VAWT was as low as 3.22 m/sec. This novel design methodology provides guidelines for obtaining optimum design configurations and can help in achieving high-fidelity analysis in the early design phase.

Investigation of unsteady pressure fluctuations and methods for its suppression for a double suction centrifugal pump

Double suction centrifugal pumps find their usage in a variety of applications because of their ability to deliver good performance at higher flowrates and heads. The main issue with these devices is the occurrence of large pressure pulsations which cause noise, vibration, and unstable operation. The present work makes an effort using steady and unsteady computational fluid dynamics (CFD) approach to minimize these pulsations and also to improve the hydraulic performance of the considered pump. The CFD methodology and obtained results were validated by the experimental data to ensure reliability of the study. Fast Fourier Transform (FFT) analysis was performed to calculate the amplitude of these pressure pulsations. A parametric study was undertaken to find the effect of impeller stagger angles in reducing these pulsations and finding the most desirable stagger angle. Then, the performance of reference non-staggered impeller design was evaluated with the use of split volute arrangement and its comparison was done with the staggered impeller design. Finally, a combination of staggered impeller design with the split volute arrangement was tested to find its utility in suppressing pressure pulsations. It was observed that the best hydraulic performance could be obtained by the staggered 30° design with reduced pulsations; however, the least pressure pulsations were delivered by the combination of staggered 30° design with the split volute. The use of CFD helped in better visualization of the inherent flow physics associated with these designs.

Sweep Effects on Fan–Intake Aerodynamics at High Angle of Attack

Abstract Sweep in a transonic fan is conventionally used to reduce design point losses by inclining the passage shock relative to the incoming flow. However, future low pressure ratio fans operate to lower Mach numbers meaning the role of sweep at cruise is diminished. Instead, sweep might be repurposed to improve the performance of critical high Mach number off-design conditions such as high angle of attack (AOA). In this article, we use unsteady computational fluid dynamics to compare two transonic low pressure ratio fans, one radially stacked and one highly swept, coupled to a short intake design, at the high AOA flight condition. The AOA considered is 35 deg, which is sufficient to separate the intake bottom lip. The midspan of the swept fan was shifted upstream to add positive sweep to the outer span. Based on previous design experience, it was hypothesized that the swept fan would reduce transonic losses when operating at high AOA. However, it was found that the swept fan increased the rotor loss by 24% relative to the radial fan. Loss was increased through two key mechanisms. (i) Rotor choking: flow is redistributed around the intake separation and enters the rotor midspan with high Mach numbers. Sweeping the fan upstream reduced the effective intake length, which increased the inlet relative Mach number and amplified choking losses. (ii): Rotor-separation interaction (RSI): the rotor tip experiences low mass flow inside the separation, which increases the pressure rise across the casing to a point where the casing boundary layer separates. The swept fan diffused the casing streamtube, causing the casing separation to increase in size and persist in the passage for longer. High RSI loss indicated that the swept fan was operating closer to the rotating stall point.

Insight Into the Interaction Between Flow Field and Acoustic Field of Turning Flow Into a Side Branch Against a Deadleg

Abstract Acoustic resonances in internal flows can cause noise, vibration, and even equipment damage. One geometry prone to acoustic resonance is a deadleg at the point where the main flow turns into a side branch. Here, we report experimental and computational fluid dynamics (CFD) studies of flow-generated pulsation in such a geometry over a wide range of mean flow velocities. Experimental results of the normalized pulsation pressure amplitudes (P*) versus Strouhal number characterized the flow–acoustic field for acoustically tuned and detuned systems and for branch to main pipe diameter ratio of 1.0. The unsteady CFD simulations revealed the characteristic volume integral of the cross-product of the vorticity field and the velocity field (ω×U) in the vicinity of the T-junction which helped in quantifying the acoustic source power for different conditions. In addition, the cross-product (ω×U) in the direction along the main line is almost exactly out of phase with the acoustic velocity at the T-junction. The pressure amplitude at the closed end of the deadleg reaches maximum when two conditions are met: (i) the system overall acoustic resonance frequency matches closely the frequency of the oscillating component of the cross-product (ω×U) characterized by a Strouhal number and (ii) the deadleg length is tuned to an odd number of ¼ wavelength of this frequency such that maximum acoustic velocity is reached at the T-junction. Synchronized images generated from the unsteady CFD simulations revealed valuable insight into the velocity and vorticity field in the region of the T-junction in support of Howe's acoustic source power equation.

Finite volume method network for the acceleration of unsteady computational fluid dynamics: Non‐reacting and reacting flows

Despite rapid improvements in the performance of the central processing unit (CPU), the calculation cost of simulating chemically reacting flow using CFD remains infeasible in many cases. The application of the convolutional neural networks (CNNs) specialized in image processing in flow field prediction has been studied, but the need to develop a neural network design fitted for CFD has recently emerged. In this study, a neural network model introducing the finite volume method (FVM) with unique network architecture and physics-informed loss function was developed to accelerate CFD simulations. The developed network model, considering the nature of the CFD flow field where the identical governing equations are applied to all grids, can predict the future fields with only two previous fields unlike the CNNs requiring many field images (>10 000). The performance of this baseline model was evaluated using CFD time series data from non-reacting flow and reacting flow simulation; counterflow and hydrogen flame with 20 detailed chemistries. Consequently, we demonstrated that (a) the FVM-based network architecture provided significantly improved accuracy of multistep time series prediction compared to the previous MLP model (b) the physic-informed loss function prevented non-physical overfitting problem and ultimately reduced the error in time series prediction (c) observing the calculated residuals in an unsupervised manner could monitor the network accuracy. Additionally, under the reacting flow dataset, the computational speed of this network model was measured to be about 10 times faster than that of the CFD solver.

Modified Savonius Wind Turbine for Wind Energy Harvesting in Urban Environments

Abstract The flow-induced rotation of the modified Savonius rotor, for which the blade consists of a semicircular profile and an elliptical shape, is studied using a series of unsteady computational fluid dynamics (CFD) simulations. This study first concentrates on the validation of the numerical scheme against Blackwell's experimental data of the conventional rotor. The computed flow physics around the modified rotor with the same diameter is then analyzed and compared with that of the conventional rotor during one rotation cycle. As the result, the modified rotor is outperforming the conventional one but keeping its unique features. The modified rotor offers exceeding performance at a tip speed ratio (TSR) greater than 0.8. The new peak of the power coefficient Cp is reached at TSR = 1.4 which is a typical operating condition of the wind turbine in urban areas. The remarkable finding is that the suppression of the flow separation on the blade is an effective way to improve the rotor's aerodynamic performance. As expected, the additional elliptical profile plays a key role in increasing the positive torque and in preventing the flow separation on the blade, especially at high TSR > 0.8. Finally, this study points to not only advances the fundamental understanding of flow mechanism around the rotor but also proposes a good practical energy harvesting application in urban environments.

Flow Separation Control on NACA0015 Airfoil Using Synchronized Jet Actuator

In this study, a novel fluidic jet actuator is designed to control flow separation on a NACA0015 airfoil at various angles of attack. The U-shaped jet actuator has two rectangular slots implemented near the leading edge of the airfoil. It is driven by a piston mechanism and operates at three excitation frequencies. Depending on the motion of the mechanism, a synchronized jet flow is generated by blowing and suction at the dual exits of the actuator slots. The experimental studies are carried out in a subsonic wind tunnel. The unsteady 2D Computational Fluid Dynamics simulations are performed by Detached Eddy Simulation with the SST k-ω turbulence model where measured jet velocities at the exits of the actuator slots are imposed as boundary conditions to mimic motion of the piston. The results at the on-mode and off-mode of the actuator are evaluated in terms of surface pressure coefficient distributions on the airfoil and averaged aerodynamic force coefficients. At low angles of attack, there is an adequate match between numerical and experimental results for the base flow without any control. At higher angles of attack, flow separation becomes considerably dominant and stall prevention by active flow control is detected especially at high excitation frequencies‎.

Investigation of propeller slipstream effects on lateral and directional static stability of transport aircraft

ABSTRACT The aerodynamic characteristics of turboprop aircraft are greatly affected by the running propellers. In this paper, propeller slipstream effects on the static lateral-directional stability characteristics of a typical twin-engine turboprop aircraft with clockwise rotating propellers were investigated through unsteady computational fluid dynamics (CFD) simulations and wind tunnel experiments. The propeller slipstream led to a significant decrease in the lateral static stability contribution of the wing-body-nacelle (WBN), and the most affected wing sections were located near the left boundary of the port propeller slipstream region. Moreover, the influence of the propeller slipstream on the lateral static stability contribution of the vertical tail plane (VTP) significantly altered the rolling moment curve slope of the entire airframe. Due to the effects of the propeller slipstream on the local dynamic pressure and therefore the effectiveness of the VTP, the aircraft showed significantly different directional static stability behaviors between the positive and negative sideslip conditions. Furthermore, it was found that the configurations with clockwise rotating propellers readily experience dramatic losses in directional static stability at large negative sideslip angles.

Experimental and computational investigation of the effect of blade sweep on acoustic characteristics of axial fan

The swept blade is one of the most efficient and practical techniques to alleviate the noise radiated from rotating fans. In this study, the swept effects of an automotive cooling fan on its acoustic characteristics were investigated using numerical and experimental approaches. Straight, forward, and backward-swept blades with a serrated shroud configuration were fabricated for the automotive cooling systems, and their performance and noise levels were measured. Moreover, measurements on the acoustic spectra were used to validate the numerical predictions. The pressure fluctuation on the cooling fan system, including the fan and shroud, was calculated from unsteady computational fluid dynamics simulation, and the acoustic signal at observer positions was predicted using an acoustic analogy. The swept effects in terms of noise reduction were compared for all three swept blades. Results indicate that the sweep angle in the forward direction can reduce the noise level of the cooling fan with a serrated shroud. Hence, the characteristics of the noise source caused by swept blades surrounding the shroud were identified in automotive cooling fans. Our findings in the present study provided significant insight into the acoustic characteristics depending on the direction of the swept blade, they can be used as a guide for designing a low-noise fan blade.

Physics-Informed Transfer Learning Strategy to Accelerate Unsteady Fluid Flow Simulations

Since the derivation of the Navier Stokes equations, it has become possible to numerically solve real world viscous flow problems (computational fluid dynamics (CFD)). However, despite the rapid advancements in the performance of central processing units (CPUs), the computational cost of simulating transient flows with extremely small time/grid scale physics is still unrealistic. In recent years, machine learning (ML) technology has received significant attention across industries, and this big wave has propagated various interests in the fluid dynamics community. Recent ML CFD studies have revealed that completely suppressing the increase in error with the increase in interval between the training and prediction times in data driven methods is unrealistic. The development of a practical CFD acceleration methodology that applies ML is a remaining issue. Therefore, the objectives of this study were developing a realistic ML strategy based on a physics-informed transfer learning and validating the accuracy and acceleration performance of this strategy using an unsteady CFD dataset. This strategy can determine the timing of transfer learning while monitoring the residuals of the governing equations in a cross coupling computation framework. Consequently, our hypothesis that continuous fluid flow time series prediction is feasible was validated, as the intermediate CFD simulations periodically not only reduce the increased residuals but also update the network parameters. Notably, the cross coupling strategy with a grid based network model does not compromise the simulation accuracy for computational acceleration. The simulation was accelerated by 1.8 times in the laminar counterflow CFD dataset condition including the parameter updating time. Open source CFD software OpenFOAM and open-source ML software TensorFlow were used in this feasibility study.

Numerical and Experimental Investigation of a Velocity Compounded Radial Re-Entry Turbine for Small-Scale Waste Heat Recovery

The energy industry must change dramatically in order to reduce CO2-emissions and to slow down climate change. Germany, for example, decided to shut down all large nuclear (2022) and fossil thermal power plants by 2038. Power generation will then rely on fluctuating renewables such as wind power and solar. However, thermal power plants will still play a role with respect to waste incineration, biomass, exploitation of geothermal wells, concentrated solar power (CSP), power-to-heat-to-power plants (P2H2P), and of course waste heat recovery (WHR). While the multistage axial turbine has prevailed for the last hundred years in power plants of the several hundred MW class, this architecture is certainly not the appropriate solution for small-scale waste heat recovery below 1 MW or even below 100 kW. Simpler, cost-effective turbo generators are required. Therefore, the authors examine uncommon turbine architectures that are known per se but were abandoned when power plants grew due to their poor efficiency compared to the multistage axial machines. One of these concepts is the so-called Elektra turbine, a velocity compounded radial re-entry turbine. The paper describes the concept of the Elektra turbine in comparison to other turbine concepts, especially other velocity compounded turbines, such as the Curtis type. In the second part, the 1D design and 3D computational fluid dynamics (CFD) optimization of the 5 kW air turbine demonstrator is explained. Finally, experimentally determined efficiency characteristics of various early versions of the Elektra are presented, compared, and critically discussed regarding the originally defined design approach. The unsteady CFD calculation of the final Elektra version promised 49.4% total-to-static isentropic efficiency, whereas the experiments confirmed 44.5%.

Influence of Pulse Characteristics on Turbocharger Radial Turbine

Abstract Turbocharging has been demonstrated as a key technology to enhance fuel efficiency in the automotive field that faces increasingly stringent emission regulations. Due to the reciprocating engine, pulsating flow feds the turbocharger turbine, which experiences conditions far from a continuous flow scenario. In this work, the effects of the characteristics of the mass flow pulse, parameterized through amplitude, frequency, and temporal gradient, are decoupled and studied via unsteady computational fluid dynamics calculations under on-engine operating conditions. First, the model is validated based on comparisons with experimental data in gas-stand conditions. Then, the effect of each parameter on the exergy budget is assessed by considering a ±10% variation with respect to a baseline pulse. The other factors defining the operating conditions (e.g., mass flow, shaft speed, and inflow exergy) are kept the same as the baseline. The adopted approach enables to completely isolate the effects of each parameter in contrast with previous literature studies. Based on the results observed, pulse amplitude is identified as the primary parameter affecting the hot-side system response in terms of turbine performance, heat transfer, and entropy generation, while frequency and temporal gradient show a smaller influence compared to it. As the pulse amplitude increases, the turbine work is reported to improve up to 9.4%. Smaller variations are otherwise observed for the frequency and temporal gradient analysis. With a 10% increase of the pulse frequency, the turbine work is registered to improve by 5.0%, while the same percentage reduction of the temporal gradient leads to an increase of the turbine work equal to 3.6%.