Decrease In Kinetic Energy Research Articles

Propagation properties of two types of sinc Schell-model beams in oceanic turbulence

Abstract The evolution of two types of sinc Schell-model (SSM) beams, each considered with both circular and rectangular symmetries, is investigated during their propagation in oceanic turbulence. The expressions for the spectral intensity and spectral coherence of the transmitted optical field are derived using the extended Huygens-Fresnel principle. Based on these expressions, numerical simulations are carried out to explore how source and turbulence parameters influence the transmitted field. The results demonstrate that the spectral intensity distribution of the SSM1 beam evolves from an initial Gaussian profile into a circular or rectangular flat-topped shape during propagation, while the SSM2 beam develops into a ring-shaped or array-like pattern. As the dissipation rate of turbulent kinetic energy decreases, or the mean square temperature dissipation rate and the strength of temperature and salinity fluctuations increase, the energy of these beams disperses from its concentrated regions to the surrounding areas, causing the characteristic intensity distributions to become blurred. Additionally, the coherence of these beams exhibits oscillatory distributions, with the SSM2 beam showing stronger oscillations compared to the SSM1 beam and displaying greater sensitivity to changes in turbulence parameters. The intensity and coherence distributions are also affected by source parameters, which play a dominant role at shorter propagation distances. However, as the distance increases, turbulence parameters gradually become the primary influence. The results presented here may be applied to oceanic optical communication and remote sensing.

Numerical and experimental study of dynamic gas–liquid separator with various viscosities

The gas–liquid separation process is important in various industries, such as electric power, aerospace, and petroleum. This study introduces an innovative, dynamic gas–liquid separator (DGLS) in which a cyclonic flow pattern is induced by blade rotation. This cyclonic flow enhances the efficiency of gas and liquid phase separation while also imparting energy to facilitate the transport of the separated fluid. Numerical simulations are used to analyze the internal flow dynamics, power requirements, and separation efficiency of this DGLS. A comparison with experimental results is conducted to validate the reliability of the numerical model. The effects of liquid-phase viscosity on the internal energy consumption and separation performance of the DGLS are explored at various flow rates. The simulation results indicate that for a given viscosity, the degassing rate of the separator decreases while the liquid removal rate increases as the inlet flow rate rises. Furthermore, it is observed that higher viscosity leads to poorer separation performance, with a decrease in turbulent kinetic energy near the rotating axis and an increase in turbulence intensity near the wall. At lower flow rates, the effectiveness of liquid-phase outlet pressurization improves with increasing viscosity. However, at higher flow rates, increasing viscosity leads to a substantial decline in energy performance and a reduction in liquid-phase outlet pressurization. The increment in turbulent kinetic energy is greater than the square of the mean velocity, indicating a positive correlation between turbulence intensity and turbulent kinetic energy. These findings not only provide a theoretical basis for the prediction of flow losses within a DGLS and the efficient design of these separators, but also provide guidance for industrial applications involving high-viscosity fluids.

Influence of the stratification parameters on the wake field of an underwater vehicle in a two-layer stratified flow

Because the ocean exhibits different stratification states in different seasons and regions, the effect of different stratification parameters on a submarine wake must be studied. In particular, to investigate such effect in a two-layer stratified flow, this study established a computational fluid dynamics (CFD) model based on the URANS equations, shear-stress transport (SST) k-ω turbulence model, and Eulerian multiphase flow model. The volume of fluid (VOF) method was adopted to implement the free-surface capture method. The working conditions of the SUBOFF model under an infinite diving depth and near the free surface were compared with those of the experiments, and the convergence of the time step and grid number under stratified flow conditions was verified. These validation steps proved the feasibility of the CFD method. Finally, the effects of the stratification parameters on the free surface waves, internal waves, and turbulent kinetic energy behind the vehicle were observed by varying the stratification parameters to achieve different working conditions. The results show that when an underwater vehicle sails in a two-layer stratified flow, the interstratified density ratio and depth of the internal wave surface affect its wake field. When the underwater vehicle sails in the water layer, with an increase in the interstratified density ratio, the free-surface roughness increases and the turbulent kinetic energy decreases. When the underwater vehicle sails in the salt water layer, the result is just the opposite.

Mechanism of Centrifugal Force Amplitude–Frequency Decoupling Exciters for Fruit Tree Vibration Harvest

Centrifugal force is often used as an exciting force for fruit vibration harvest. However, the magnitude of centrifugal force varies quadratically with angular velocity. When the frequency of excitation force remains constant, the amplitude of vibration force cannot be freely adjusted. This study achieves decoupling of the amplitude and frequency of centrifugal force by varying the eccentricity of the eccentric block. Different combinations of eccentric blocks with varying quantities and parameters enable the creation of different types of centrifugal force amplitude–frequency decoupling exciters. Both the amplitude and frequency of excitation force produced by these exciters can be freely adjusted. Furthermore, a physical prototype of a symmetrical dual eccentric block exciter with centrifugal force amplitude–frequency decoupling is developed and tested. It is found that when the exciter frequency or excitation force amplitude remains constant, the vibration acceleration amplitude generated by the exciter changes by adjusting the eccentricity of the eccentric blocks. As the eccentricity of the eccentric blocks decreases, their moment of inertia and kinetic energy decrease. Utilizing mechanisms to adjust the eccentricity of the eccentric block’s center of mass to the rotation axis achieves the dynamic adjustment of the size and frequency of centrifugal force.

Effects of wall heating on wall pressure fluctuations and flow noise in a low-Reynolds-number turbulent channel flow with temperature-dependent viscosity

Wall pressure fluctuations and flow noise substantially degrade sonar detection performance and the acoustic stealth performance of underwater vehicles. This paper numerically investigates the effects of wall heating on wall pressure fluctuations in turbulent channel flow of water with temperature-dependent viscosity, exploring a novel method for controlling wall pressure fluctuations and flow noise in underwater vehicles. Large-eddy simulation (LES) is employed for the numerical calculation of the flow field, while a hybrid method combining LES with Lighthills acoustic analogy is employed to predict flow noise. The numerical results show that when the temperature difference between the wall and the incoming flow is 30 K and 50 K, the peak root-mean-square pressure fluctuations decrease by 6.76% and 8.91%, respectively. Wall heating stabilizes the pressure field near the wall, with the spectral levels of wall pressure fluctuations showing average decreases of approximately 1 dB and 2 dB. Wall heating weakens the energy-containing structures of wall pressure fluctuations and increases the overall convection velocity by 1.22% and 3.81%, respectively. Flow structure analysis reveals that the weakening of energy-containing structures results from the suppression of the vortex structures in the near-wall region. In the wall heating cases, peak turbulent kinetic energy decreases by 12.6% and 15.8%, respectively. Moreover, the sound pressure level of flow noise decreases with increasing wall temperature, with the maximum noise reduction exceeding 3 dB. Previous studies have not yet explored the effects of viscosity reduction caused by wall heating on wall pressure fluctuations and flow noise. This study demonstrates that wall heating is a promising method for reducing wall pressure fluctuations and flow noise.

A new non‐equilibrium modification of the k−ω$$ k-\omega $$ turbulence model for supersonic turbulent flows with transverse jet

AbstractThe goal of this research is to propose a new modification of a non‐equilibrium effect in the turbulence model to better predict high‐speed turbulent flows. For that, the two local compressibility coefficients are included in the balance production/dissipation terms in a specific dissipation rate equation. The specific dissipation rate reacts to changes in the local Mach number and density through these local coefficients. The developed model is applied to the numerical simulation of the spatial supersonic turbulent airflow with round hydrogen injection. In that, the effects of the proposed turbulence model on the flow field behavior (shock wave and vortex formations, shock wave/boundary layer interaction, and mixture layer) are studied via the solution of three‐dimensional Favre‐averaged Navier–Stokes equations with a third‐order Essentially Non‐Oscillatory scheme. A series of numerical experiments are performed, in which an allowable range of local constants by comparing results with experimental data is obtained. The non‐equilibrium modification by simultaneous decrease of the turbulence kinetic energy and increase of the specific dissipation rate gives a good agreement of the hydrogen depth penetration with experimental data. Also, the numerical experiment of the supersonic airflow with a nitrogen jet shows wall pressure distribution is consistent well with experimental data.

Molecular dynamics and experimental analysis of energy behavior during stress relaxation in magnetorheological elastomers

The diverse applications of magnetorheological elastomer (MRE) drive efforts to understand consistent performance and resistance to failure. Stress relaxation can lead to molecular chain deterioration, degradation in stiffness and rheological properties, and ultimately affect the life cycle of MRE. However, quantifying the energy and molecular dynamics during stress relaxation is challenging due to the difficulty of obtaining atomic-level insights experimentally. This study employs molecular dynamics (MD) simulation to elucidate the stress relaxation in MRE during constant strain. Magnetorheological elastomer models incorporating silicone rubber filled with varying magnetic iron particles (50–80 wt%) were constructed. Experimental results from an oscillatory shear rheometer showed the linear viscoelastic region of MRE to be within 0.001–0.01% strain. The simulation results indicated that stress relaxation has occurred, with stored energies decreased by 8.63–52.7% in all MRE models. Monitoring changes in energy components, the highest final stored energy (12,045 kJ) of the MRE model with 80 wt% Fe particles was primarily attributed to stronger intramolecular and intermolecular interactions, revealed by higher potential energy (3262 kJ) and van der Waals energy (− 2717.29 kJ). Stress relaxation also altered the molecular dynamics of this MRE model as evidenced by a decrease in kinetic energy (9362 kJ) and mean square displacement value (20,318 Å2). The MD simulation provides a promising quantitative tool for elucidating stress relaxation, preventing material failure and offering insights for the design of MRE in the nanotechnology industry.

Structure evolution of the silica glass under the vibration field through molecular dynamics simulations

AbstractSilica glass has found wide applications, including space shuttle windows, optical fibers, and deep ultraviolet light lens elements, due to its excellent optical, electrical, and mechanical properties. However, understandings of its structure change under the vibration field are limited in literature. In this work, the structure of silica glass and its behavior under the vibration field have been investigated through molecular dynamics simulations. The short and medium‐range structures, including coordination number, Qn species distribution, pair distribution function, and bond angle distribution, were analyzed. It was found that the overall and local structures of silica glass showed periodic changes under the vibration field. The root‐mean‐square displacements as well as the kinetic energies of the atoms in the system were further analyzed. The results show that there is a periodic transformation of kinetic and potential energies. In addition, the kinetic energy decreases and is converted into the thermal energy during the vibration, which is confirmed by the increase of the system temperature. This can explain the thermoelastic loss mechanism in energy dissipation from literature. This work reveals the structure evolution and energy change of glass under the vibration field from atomistic level, which provides important understandings for related researches.

Influence of wind direction on flow over a cliff and its interaction with a wind turbine wake

This work investigates the effect of wind direction on the flow over a cliff and its interaction with the wake of a wind turbine sited on the cliff. The cliff is modeled as a forward-facing step, and five wind directions are tested (θ=0∘, 15∘, 30∘, 45∘, and −45∘), where 0∘ represents a wind direction perpendicular to the cliff edge. The flow becomes increasingly three-dimensional with the increase in the wind direction magnitude and a cross-stream flow separation develops from the cliff leading edge. The turbulence kinetic energy decreases for wind directions higher than 15∘, which is due to the absence of the streamwise flow separation for higher wind directions. The cross-stream flow development in the base flow affects the shape of the turbine wake. A two-dimensional Gaussian fit is performed on the wake velocity deficit, which shows a slight departure from self-similarity in the lateral direction. The wake recovery slows down for wind directions higher than 15∘, which is consistent with the decrease in the wake growth rate for θ>15∘. The wake shows higher deflection and tilt angle for higher wind directions. Analysis of the streamwise momentum in the wake reveals that the advection terms play a role in slowing the wake recovery for higher wind directions. Published by the American Physical Society 2024

Molecular dynamics simulation of bulk nano-oxygen-bubble fuel under high-pressure transport and sudden pressure drop process

Aiming at the injection process of bubbly flow fuel, the molecular dynamics simulation was performed to study the change of bulk nano-oxygen-bubble (BNB) fuel during high-pressure transport and sudden pressure drop process. The static processes of BNB fuel containing different oxygen molecules numbers are explored in depth at normal temperature and pressure and pressure increase as well as the dynamic process under high-flow-rate-coupled sudden pressure drop. The results show that after adding BNB, the BNB contour increases first and then decreases. Increasing the number of oxygen molecules added at normal temperature and pressure shortens the BNB stabilization time and improves BNB stability. The BNB inner density in fuel is much smaller than that in water. Under high-pressure condition, the BNB which can be stabilized in the fuel at normal temperature and pressure quickly dissolves and disappears due to the increase in solubility of oxygen, resulting in a decrease in the oxygen molecule potential energy. Increasing the number of oxygen molecules added has only a weak slowing down effect on the dissolution rate. During the high-speed jetting of fuel at the nozzle, BNB promotes fuel droplet fragmentation and increases the oxygen concentration around the fuel droplet. In this process, the oxygen molecules do work on the fuel and their kinetic energy decreases. Increasing the number of oxygen molecules added reduces fuel breakup time and improves the quality of gas mixture formed. The results of this study can provide a reference for the micro-mechanism of BNB on improving the atomization characteristics of bubbly flow fuel.

Mixing of a cylindrical gravity current in a stratified ambient

Simulation results from direct numerical simulations (DNSs) of cylindrical gravity currents propagating into a linearly stratified ambient with stratification strengths ranging from 0 to 0.8, at a moderate Reynolds number of Re=3450 are presented. The simulations are based on the incompressible Navier–Stokes equations, assuming small density differences such that the Boussinesq approximation is valid. The density of the ambient fluid increases linearly from the top (ρ0) to the bottom (ρb) of the domain. A comparative analysis is conducted between the stratified cases and the unstratified case to investigate the impact of ambient stratification strength on the mixing behaviour of cylindrical gravity currents. The energy conversion processes are analysed using the mechanical framework proposed by Winters et al. (1995). The energy budget is formulated by considering gravitational available potential energy, and the evolution of potential energy due to reversible stirring and irreversible diapycnal mixing in the system. The findings reveal a decrease in available potential energy and kinetic energy with increasing stratification strength, indicating lower energy exchange for gravity currents propagating in the stratified environment. Instantaneous and cumulative mixing efficiency calculations during the slumping phase indicate that Kelvin–Helmholtz billow play an important role in stirring the heavy fluid and causing irreversible mixing with the ambient fluid.

Cylinder flow and noise control by active base blowing

An extensive experimental investigation was undertaken to control the flow and noise characteristics influenced by vortex shedding from a circular cylinder by implementing air blowing at the base of the cylinder. The study synchronised near-field pressure and far-field noise measurements with the wake velocity field to understand the noise reduction mechanism of base blowing. Surface pressure fluctuations were measured using pressure taps distributed around the cylinder's circumference through a remote-sensing method, while velocity measurements were obtained using planar particle image velocimetry at the midspan to examine the flow dynamics. The study unveiled the crucial role of near-field pressure, particularly induced at the shoulders of the cylinder, in generating far-field noise. The rapid vertical flow movement, arising from the interaction between shear layers, was identified as a mechanism responsible for inducing surface pressure fluctuations. This phenomenon occurred as high-momentum fluid moved from the free stream into the interior of the vortex-formation region. By applying base blowing, a remarkable reduction in both near-field pressure and far-field noise was achieved at the fundamental vortex-shedding frequency, with reductions of approximately 20 and 25 dB, respectively, compared with the baseline. Additionally, base blowing caused the shear layers to roll up farther downstream than in the baseline by decreasing the entrainment of fluid-bearing opposite vorticity by the shear layer upstream of the growing vortex. Consequently, there was a substantial decrease in turbulent kinetic energy and Reynolds stress near the cylinder, resulting in slower vertical flow movement and weaker near-field pressure.

Passive control of the condensing flows in the three-dimensional steam turbine blade using a suction technique

A great amount of thermodynamic losses and mechanical damages in industrial equipment occur due to the condensation phenomenon and two-phase flows in such equipment. In this study, supercooled vapor suction has been passively used in the 3D (three-dimensional) steam turbine stationary blade. Supercooled vapor suction is one of the techniques used in turbines for resisting corrosion and erosion. For the supercooled flow suction, the design is as follows: an embedded channel inside the turbine blade in the nucleation zone, which has the utmost non-equilibrium mode; furthermore, the impacts of the location and surface of the channels devised in the turbine blade for supercooled vapor suction on the following parameters have been investigated: the two-phase flow, the suction ratio, condensation losses, erosion ratio, the average droplet growth, and kinetic energy. Based on the results, in the optimal case (case F), the condensation losses, erosion ratio, average droplet radius, and kinetic energy decrease by 3%, 24%, 6.5%, and 2%, respectively; also, the suction ratio is 3.6%. The present research reveals that the supercooled vapor suction, due to a decrease in the surface necessary for the condensation, decreases turbine blade corrosion and erosion. This fact can provide the turbine designers with beneficial information.

SDSS-IV MaNGA: calibration of astrophysical line-widths in the Hα region using HexPak observations

ABSTRACT We have re-observed $\rm \sim$40 low-inclination, star-forming galaxies from the MaNGA survey (σ ∼ 65 km s−1) at ∼6.5 times higher spectral resolution (σ ∼ 10 km s−1) using the HexPak integral field unit on the WIYN 3.5-m telescope. The aim of these observations is to calibrate MaNGA’s instrumental resolution and to characterize turbulence in the warm interstellar medium and ionized galactic outflows. Here we report the results for the Hα region observations as they pertain to the calibration of MaNGA’s spectral resolution. Remarkably, we find that the previously reported MaNGA line-spread-function (LSF) Gaussian width is systematically underestimated by only 1 per cent. The LSF increase modestly reduces the characteristic dispersion of H ii regions-dominated spectra sampled at 1–2 kpc spatial scales from 23 to 20 km s−1 in our sample, or a 25 per cent decrease in the random-motion kinetic energy. This commensurately lowers the dispersion zeropoint in the relation between line-width and star-formation rate surface-density in galaxies sampled on the same spatial scale. This modest zero-point shift does not appear to alter the power-law slope in the relation between line-width and star-formation rate surface-density. We also show that adopting a scheme whereby corrected line-widths are computed as the square root of the median of the difference in the squared measured line width and the squared LSF Gaussian avoids biases and allows for lower signal-to-noise data to be used reliably.

DETERMINATION OF THE DROP SIZE AND DISTRIBUTIONS IN SWIRL INJECTION IN CROSS FLOWS, IMPINGING, AND EFFERVESCENT INJECTORS

We have extended the primary atomization analysis to swirl injection in cross flows, impinging, and effervescent injectors. Using the integral form of the conservation equations, the drop size can be expressed in terms of injection and fluid parameters, the main variable being the liquid and gas velocities. Using the measured velocities as inputs to this <i>D</i><sub>32</sub>-equation, good agreements with experimental data are found for the drop size in the three spray geometries. Underlying physical mechanisms for the drop formation are also revealed from the analysis. The aerodynamic interaction between the swirl spray and cross flow results in reduction in momentum, with a corresponding decrease in kinetic energy that appears as surface tension of energy of many small droplets. Similarly, cancellation of the lateral momentum in impinging jets and internal deceleration in effervescent injectors are the key primary atomization routes. The use of the analytical drop size-velocity correlation has also been demonstrated for swirl sprays in cross flows. Therefore, this approach can be used to predict the drop size and distributions in different spray geometries, with appropriate changes in the velocity input terms and fluid properties.

Space-resolved average kinetic energy of ion swarms in a uniform electric field.

A pulse of noninteracting charged particles in an unbounded gas, exposed to a low, constant, homogeneous electric field, was studied in both space and time using a Monte Carlo simulation technique. The difference in electrical potential between the leading and trailing edges of the swarm results in the space-resolved average ion kinetic energy becoming a linearly increasing function of space. This Letter analyzes whether the average ion kinetic energy at the leading edge reaches a stationary value during the spatiotemporal evolution of the swarm, as has been considered so far. When the swarm's mean kinetic energy reaches a steady-state value, indicating that an energy balance is established over time, the gains (from the field) and losses (due to collisions) are nonuniform across space. The local power balance is negative at the front of the swarm and positive at the tail. Cooling the ions at the front and heating the ions at the tail results in a decrease in the average ion kinetic energy at the front and an increase at the tail. Thus, it can be concluded that stationary values of average ion kinetic energy do not exist at the leading and trailing edges during the evolution. Instead, they tend to approach the swarm's mean kinetic energy as t→∞.

Quantitative proton radiography and shadowgraphy for arbitrary intensities

Charged-particle radiography and shadowgraphy data can be directly inverted to obtain a line-integrated transverse Lorentz force or a line-integrated transverse refractive index gradient if intensity modulations due to scattering and absorption are negligible, and angular deflections are small. We develop a new direct-inversion algorithm based on plasma physics and compare it to a new Monge–Ampère code and an existing power diagram code (Kasim et al., 2017). The measured or source intensity is represented by electrons subject to drag, and the other intensity by fixed ions. The decrease in kinetic plus electrostatic energy determines convergence. The displacement of the electrons from their initial to their equilibrium positions determines the line-integrated force or refractive index gradient. We have implemented two approaches: PIC (particle in cell) and Lagrangian fluid, in 1-D and 2-D. The PIC code works for arbitrary intensities, can work efficiently in parallel, and can make use of existing codes. The Lagrangian code requires less memory and is faster than the PIC code without massively parallel processing, but fails in 2-D for large intensity modulations. The Monge–Ampère code is by far the fastest in 2-D, without massively parallel processing, but fails for intensities with large voids, high contrast ratios and large deflections across the boundaries, and could not obtain the degree of convergence possible with the PIC code. The power diagram code was by far the slowest and most memory intensive, and failed for large peaks in the measured intensity.

Numerical study on reaction and heat transfer of supercritical aviation kerosene with pyrolysis and steam reforming in a corrugated cooling channel

Coking and heat transfer deterioration of supercritical aviation kerosene pose grave challenges to regenerative cooling of scramjet engines. In the present study, reaction and heat transfer characteristics of supercritical China aviation kerosene No. 3, RP-3 undergoing simultaneous pyrolysis and steam reforming reactions in a corrugated channel are numerically studied. Compared with reacting flow of RP-3 in the smooth channel, temperature and coke deposition are much lower in majority part of the corrugated channel. The maximum temperature difference between the smooth and corrugated channels is up to 300K. The maximum heat transfer coefficient in the corrugated channel is almost three times of that in the smooth channel under the same condition. However, low-velocity and high-temperature zones are formed near the corrugated micro-structures and cause coke accumulation and heat transfer deterioration along the flow direction of the corrugated channel. With the increase of wall heat flux, both temperature and velocity increase significantly in the corrugated channel. The conversion of RP-3 and formation of coke are also enhanced with increasing wall heat flux. Moreover, the total heat transfer coefficient first increases and then decreases with wall heat flux. The maximum total heat transfer coefficient increases from 4000W/m2∙K to 18,000W/m2∙K with wall heat flux increasing from 0.3MW/m2 to 1.8MW/m2. Periodic wavy structures are found at the interface between the corrugated micro-structure and the bulk flow, which is pronounced when wall heat flux is 1.3MW/m2 or above. With the increase of flow time, local turbulent kinetic energy decreases due to the interaction between the corrugated micro-structures and the wavy structures. The interaction between the corrugated structures and complex reaction and heat transfer leads to intersection of the distributions of temperature and coke in the smooth and the corrugated channels. An empirical heat transfer correlation formula is obtained as Nu=0.1Re0.65Pr1.94 for RP-3 reacting flow in the corrugated channel. The study provides better insight into interaction mechanism between chemically reacting flow and micro corrugated structures.

Antarctic Bottom Water in the Vema Fracture Zone

AbstractA section of 46 CTD/Lowered Acoustic Doppler Current Profiler stations along the Vema Fracture Zone (VFZ) was made for the first time with a repeat of the transverse section on the main sill (at 41° W) for the sixth time. Potential temperature of Antarctic Bottom Water when it flows into the fracture increases from 1.3°С to 1.6°C. This temperature increase is much smaller than in the Romanche Fracture Zone because in the VFZ there are not many transverse sills that force the flow to become turbulent. A zone with minimal velocities of the bottom flows exists in the western part of the VFZ up to the main sill. A current with velocities of 0.25 m/s flows above the low velocity zone at a depth of about 4,000 m. Underwater spillways with hydraulically controlled flow of bottom water down the slope from 4,500 m to 5,000 m at speeds up to 0.40 m/s were found east of the sill (in the central and southern channels). The bottom current accelerates as it flows down, but then its kinetic energy decreases. The bottom current slows down and mixes with surrounding waters. A thin (∼30 m) bottom flow descends further to the deep depression. In the southern channel of the VFZ, bottom water flows into a deep (5,400 m) basin. The coldest and densest water reaches this depression during rare inflows.

Bacterial turbulence in gradient confinement

We investigate a novel form of non-uniform living turbulence at an extremely low Reynolds number using a bacterial suspension confined within a sessile droplet. This turbulence differs from homogeneous active turbulences in two or three-dimensional geometries. The heterogeneity arises from a gradient of bacterial activity due to oxygen depletion along the droplet’s radial direction. Motile bacteria inject energy at individual scales, resulting in local anisotropic energy fluctuations that collectively give rise to isotropic turbulence. We find that the total kinetic energy and enstrophy decrease as distance from the drop contact line increases, due to the weakening of bacterial activity caused by oxygen depletion. While the balance between kinetic energy and enstrophy establishes a characteristic vortex scale depending on the contact angle of the sessile drop. The energy spectrum exhibits diverse scaling behaviors at large wavenumber, ranging from k −1/5 to k −1, depending on the geometric confinement. Our findings demonstrate how spatial regulation of turbulence can be achieved by tuning the activity of driving units, offering insights into the dynamic behavior of living systems and the potential for controlling turbulence through gradient confinements.