Velocity Plots Research Articles

Melting dynamics analysis of a multi-tube latent heat thermal energy storage system: Numerical study

This numerical study investigates the melting dynamics of paraffin wax as a phase change material (PCM) in a multi-tube latent heat thermal energy storage system (MT-LHTESS). The performance of an arrangement with four tubes is compared with a concentric single tube arrangement keeping the same cross-section area of heat transfer fluid tubes and the same PCM quantity. Four longitudinal fins of two types are also incorporated to further improve the melting. Thirteen cases with different arrangements of tubes and fins are compared in this study. The study attempts to select a suitable arrangement of the tubes. A two-dimensional enthalpy-porosity model in ANSYS-Fluent is used to solve the governing equations. The melting results are depicted as the contours of liquid fraction, temperature, and flow streamlines. The transient performance is assessed based on progress plots of liquid fraction and average domain velocity. It is observed that splitting into multiple tubes and using fins enhance the melting performance. The generation and coalescence of small vortices in the molten PCM accelerate the melting performance. The staggered array, larger eccentricity, and (+ type) finned tubes outperform their counterparts. The lowest melting time is observed in Case 2(+), having four staggered tubes, at 30 mm eccentricity, and with (+ type) fins. This case takes 75 min for complete melting, and 1411.1 kJ/m heat at a rate of 322 W/m is stored. The melting time gets reduced by 53.3–71.1% using four tubes and by 65.78–83.33% using finned four tubes as compared to the single tube case.

Magneto-Oldroyd-B fluid flow over an exponentially accelerated vertical porous plate with heat source and reactive agents

ABSTRACT The present research work describes about flowing magnetohydrodynamic generalized Oldroyd-B liquid model in an exponentially accelerated vertical porous boundless device with heat source and reacting species and heat source. The fully developed Oldroyd-B fluid model is stimulated by heat source/sink and species reaction and vertical device under the influence of gravity. The physical flow equation is modelled in the form of partial derivative which is mutated into the dimensionless partial derivative equations by invoking suitable non-dimensional variables. The partial system of derivative equations is tackled by employing perturbation technique. The outcomes for the velocity flow field, thermal and species distributions are exhibited graphically. Computed outcomes for the plate friction, heat gradient and Sherwood number are provided in table. Furthermore, correlation in terms of validation has been tabulated. Some obtained results show that an increase in heat source and time reduces velocity plots but increase the rate of particle temperature. Owing to the Lorentz force produced by the imposed magnetic field, the velocity alongside velocity degenerates. Time parameter compliments the fluid temperature, particle concentration and fluid transport. The heat transfer rate accelerates with higher Prandtl number and heat source, but mass transfer rate retards with higher Schmidt number.

Effectiveness of splitter plate to control fluid forces on a circular obstacle in a transient flow: FEM computations

The reliability of the usage of a splitter plate (passive control device) downstream of the obstacle, in suppressing the fluid forces on a circular obstacle of diameter D = 0.1;;{text{m}} is studied in this paper. The first parameter of the current study is the attachment of a splitter plate of various lengths (L_{i} ) with the obstacle, whereas the gap separation (G_{i} ) between the splitter plate and the obstacle, is used as a second parameter. The control elements of the first and second parameters are varied from 0.1 to 0.3. For the attached splitter plates of lengths 0.2 and 0.3, the oscillatory behavior of transient flow at Re = 100 is successfully controlled. For the gap separation, 0.1 and 0.2 similar results are obtained. However, it is observed that a splitter plate of too short length and a plate located at the inappropriate gap from the obstacle, are worthless. A computational strategy based on the finite element method is utilized due to the complicated representative equations. For a clear physical depiction of the problem, velocity and pressure plots have been provided. Drag and lift coefficients the hydrodynamic benchmark values are also evaluated in a graphical representation surrounding the obstacle’s peripheral surface as well as the splitter plate. In a conclusion, a splitter plate can function to control fluid forces whether it is attached or detached, based on plate length and gap separation between obstacle and plate, respectively.

Passive Control of Hydrodynamic Forces on a Circular Obstacle in a Transient Flow: FEM Computations

Hydrodynamic forces are crucial in engineering applications; therefore, various research initiatives have been conducted to limit them. In this research, a passive control technique to investigate the fluid forces acting on a circular cylinder in a laminar flow regime is studied. The reliability of the usage of a splitter plate (passive control device) downstream of the obstacle in suppressing the fluid forces on a circular obstacle of diameterD=0.1is presented. The first parameter of the current study is the attachment of splitter plates of various lengths(Li)with the obstacle, whereas the gap separation(Gi)between the splitter plate and the obstacle is used as a second parameter. The control element of the first and second parameters are varied from0.1to0.3. For the attached splitter plates of lengths0.2and0.3, the oscillatory behavior of transient flow atRe=100is successfully controlled. For the gap separations0.1and0.2, the suppression of vortex shedding is also observed. However, it is observed that a splitter plate of too short length and a plate located at an inappropriate gap from an obstacle are worthless. Moreover, the present study is extended for power-law fluid in the same domain, and maximum drag reduction is achieved using the same strategy as for Newtonian fluid. The finite element method is utilized as a computational strategy for complicated nonlinear governing equations. For a clear physical depiction of the problem, velocity and pressure plots have been provided. It is concluded that the presence of a splitter plate has suppressed the vortex shedding and the flow regime turns out to be steady, as is evident from the nonoscillatory drag and lift coefficients.

Identifying Merging Galaxies in MaNGA using H-a and Hi Observations

Reliable methods that could recognise and distinguish galactic mergers are important for better understanding of galaxy evolution. This paper explores the feasibility of using observations on Hα and HI as a method to identify mergers. Sixty sample galaxies were carefully selected from the MaNGA DR15 database and cross-checked with the MaNGA Deep Learning DR15 Morphology to determine the merger signature. The chosen galaxies were divided into two groups, where galaxies with P M E RG < 0.5 were selected as non-merging galaxies and galaxies with P M E RG > 0.8 were selected as mergers. The Hα emission line plot and Hα velocity maps were obtained from the MaNGA DR15 database while HI data comes from HI-MaNGA DR1 catalogue for all 60 galaxies. Seventeen of the 30 merging galaxies have more than Hα blobs (28.3% of the 60 galaxies) compared to 14 of the 30 non-merging galaxies (23.3%). Fourteen of the mergers (23.3% of 60 galaxies) have asymmetric Hα velocity plots compared to 8 of the non-mergers. Thirteen of the mergers have a well-defined HI peak (21.7%) versus 11 of the non-merging galaxies (18.3%). These parameters were found to be a feasible new method in determining merging galaxies in the universe.

A New Explicit Numerical Schemes for Time-Dependent PDEs with Application to Pressure Driven Fluid Flow in a Rectangular Duct

A modified class of temporal discretization schemes for partial differential equations (PDEs) is proposed, explicit and second to fifth-order accurate in time. In time, the stability region of the proposed modified second-order scheme is larger than the standard second-order Adams–Bashforth method constructed on two time levels. A modification made for the Du Fort–Frankel method was also implemented in the proposed second-order scheme, which permits the little larger stability region, but the scheme becomes first-order accurate. Since the Du Fort–Frankel method cannot be employed without a modification of averaging in time levels, the proposed second-order scheme can be used without any modification. The proposed modified scheme with different orders in space and second orders in time was implemented for heat and mass transfer of chemically reactive fluid flow in a rectangular duct. The flow is generated due to applying different pressure gradients. The contour plots of velocity, temperature, and concentration profiles are portrayed at different pressure gradients; Péclet number in heat transfer, Péclet number in mass transfer, reaction parameter, and at different times. In addition, stability and convergence conditions for the considered system of linear and non-linear PDEs consisting of non-dimensional momentum, energy, and concentration equations were found for two cases. The displayed graphs depict the transfer of heat in the fluid, which rises due to heated boundaries, and the transfer of mass in the fluid at various moments. Classical models can be solved using the proposed method, which has a faster convergence rate than the standard or classical approach. This approach is illustrated through computer simulations that demonstrate its key computational features. It is believed that the data presented in this study will serve as a useful source for future fluid flow investigations to be conducted in an industrial setting within an enclosed area.

A comparative study between Amontons–Coulomb and Dieterich–Ruina friction laws for the cyclic response of a single degree of freedom system

This study aims at assessing the predictive performance of the Amontons–Coulomb law to reliably predict the cyclic response, inclusive of stick–slip, of a single degree of freedom system in contact with the ground through two versions (steady-state and rate-and-state) of a regularized Dieterich–Ruina law. The assessment is carried out by defining a cost function and a physics-based constraint that enable the identification of the corresponding optimal coefficients of the Amontons–Coulomb law through a multi-start constrained non-linear optimization. The comparative study starts with a sensitivity analysis, aimed at first identifying the most meaningful model parameters for the Dieterich–Ruina law. Subsequently, the cyclic dynamic responses provided by both friction laws are analysed for varying model parameters, and characteristic features are observed within the dynamic forcing–displacement graph and the friction force–velocity plot, that could be directly linked to one friction model or the other. The sensitivity analysis led to the definition of a cost function expressed in terms of the displacement and velocity response differences and a constraint based on the phase difference. The optimization study identified areas of the Dieterich–Ruina’s parameter space for which the Amontons–Coulomb law can reliably be used to predict a cyclic stick–slip response. The relevance of these results with respect to problems of modelling and identification of friction are discussed.

Impact Of Porous-Media Topology On Turbulent Fluid Flow: Time-Resolved PIV Measurements

An investigation of the interactions between a turbulent duct flow above a 3D porous medium with a periodic topology is reported. Both spatially and temporally resolved point measurements of velocity in the free flow and at the interface of the porous medium using the Particle Image Velocimetry (PIV) technique are presented. A Schwarz Primitive triply periodic minimal surface (TPMS) with a frequency of f = Π/20 printed from polyamide PA12 with a porosity of ϕ = 0.92 was investigated as a porous structure. The periodicity of the model results in two different topologies, hill- and valley-alignment, each of which represent a measurement plane. These different alignments show a strong influence on the turbulent flow above the porous me dium. In addition to the time-averaged velocity field for the two alignments, velocity profiles as well as turbulent kinetic energy profiles at selected positions in flow direction are also shown. The influence of the turbulent channel flow on the porous model is shown by a contour plot of the time-resolved velocity, where this represents the turbulent fluctuation at a point in t ime. For the time-resolved plot, the same influence of the different topology to the respective alignments is shown. With these time-resolved measurements, transient flow processes could be resolved, such as the detachment and attachment of the flow to the porous surface, which are also shown in this paper. These measurements provide an insight into the mechanism of energy, mass and momentum transfer at the interface between the free stream and the porous medium. The results presented are useful for further understanding of turbulent flows on flush mounted complex 3D structures and the influence of the periodic surface on the free flow.

Influence of sidewalls on three-dimensional turbulent wall jet: An experimental and numerical approach

In this study, with the help of with and without sidewall configurations, experimental and numerical approaches are utilised to investigate the sidewall influence on a three-dimensional turbulent wall jet. The mean flow profile of the three-dimensional turbulent wall jet is measured through experimental method and compared with the numerical results. In addition, the numerical method is used to characterise the turbulence characteristics of the wall jet for both the configurations. A 200 mm square nozzle (height h=20 ± 0.5 mm) is used to generate the developing jet exit profile for the experimental results. The Reynolds number based on the jet exit velocity and nozzle height is 25,000. The numerical results are obtained by solving the Reynolds Average Navier stokes (RANS) equations with low Reynolds number k−ε turbulence models proposed by Yang and Shih and Launder and Sharma. The experimental results are obtained by a single probe hotwire anemometer and a K-type thermocouple. It is observed that the sidewall affects the temperature distribution just after the potential core region x/h=5 whereas the velocity distribution is affected in the fully developed region after the downstream location x/h=22.5. Sidewalls drastically influenced the thermal and velocity decay in wall-normal and lateral directions. It is found from the numerical simulation that the decay of maximum streamwise velocity is increased by 9%, whereas centerline temperature decay is decreased by 25% in sidewall configuration as compared to without sidewall configuration. The contour plots of temperature and velocity also exhibit the sidewall effect on the whole domain. The Reynolds shear stress <u′v′> dominates in the vertical jet centerline plane atz=0, whereas <u′w′> dominates in the lateral direction at ymax plane in both the configurations. On the vertical jet centerline plane at z=0, Reynolds shear stress <u′v′> is nearly increased by 10% in the presence of sidewall compared to without sidewall configuration. The entrainment of the ambient fluid initially decreases, but after the downstream location x/h=22.4, it increases for the case of the sidewall compared to the corresponding case without the sidewall. This happens owing to an increase in maximum turbulent kinetic energy generation inside the flow domain by 10%. The turbulent heat flux <T′V′> dominates in lateral and wall-normal shear layers in both the configurations. The correlations of decay of temperature and velocity are also suggested through numerical techniques.

Comparative study of solar air heater (SAH) roughened with transverse ribs of NACA 0020 in forward and reverse direction

Experimental and Numerical investigation of heat transfer and fluid flow characteristics is carried out for SAH duct (aspect ratio, W/H = 10:1) with transverse ribs of different cross-sections (square, semi-circular and symmetric half NACA 0020 in both forward and reverse orientations) on one of its broad wall. Solutions are obtained using SIMPLE algorithm for coupling of pressure and velocity, while for discretization of momentum and energy equations upwind scheme of second order is used in commercial ANSYS software. Nusselt number ( Nu ) and friction factor (f) are evaluated for Reynolds number (Re) ranging from 6000 to 18000, fixed relative roughness pitch (P/e = 12) and relative roughness height (e/D = 0.05). The highest value of ( Nu ) is found for ribs of semi-circular cross-section while minimum (f) is observed for forward oriented symmetric half NACA 0020. The highest thermo-hydraulic performance parameter is achieved at Re = 6000 with symmetric half NACA 0020 rib roughness when used in reverse orientation. Contours plots of temperature, velocity streamlines and pressure variation yielded important results for understanding the physical phenomenon inside the SAH. The numerical outcomes are validated with experimental results.

Numerical simulations for heat transfer in peristalsis of Bingham fluid utilizing partial slip conditions

The buoyancy-assisted peristaltic motion of viscoplastic fluid in a vertical channel is revisited by accounting partial slip effect at the channel boundaries. Accompanying heat transfer problems due to fluid friction is addressed through the temperature jump assumption. The governing system formed under lubrication approximation is coupled owing to the existence of buoyant force. The system contains a parameter , measuring the fluid yield stress. Moreover, in contrast to the no-slip case, the boundary conditions are Robbin-type conditions and nonlinear in the axial velocity component. An easy-to-use yet reliable package NDSolve of the software MATHEMATICA is utilized to solve the problem for broad ranges of Bingham number and slip coefficients. Plots of stream function, velocity, and temperature are generated, which clearly depict that the yield stress combined with partial slip assumption considerably affects the flow phenomena. To illustrate heat transfer rates, the expression of heat transfer rate is analyzed across the channel walls under different controlling parameters.

Protostellar discs subject to infall: a one-dimensional inviscid model and comparison with ALMA observations

ABSTRACT A new one-dimensional, inviscid, and vertically integrated disc model with prescribed infall is presented. The flow is computed using a second-order shock-capturing scheme. Included are vertical infall, radial infall at the outer radial boundary, radiative cooling, stellar irradiation, and heat addition at the disc-surface shock. Simulation parameters are chosen to target the L1527 IRS disc which has been observed using Atacama Large Millimeter Array (ALMA). The results give an outer envelope of radial infall and uϕ ∝ 1/r which encounters a radial shock at rshock ∼ 1.5 × the centrifugal radius (rc) across which the radial velocity is greatly reduced and the gas temperature rises from a pre-shock value of ≈25 to ≈180 K over a spatially thin region calculated using a separate shock structure code. At rc, the azimuthal velocity uϕ transitions from being ∝ 1/r to being nearly Keplerian. These results qualitatively agree with recent ALMA observations which indicate a radial shock where SO is sublimated as well as a transition from a uϕ ∼ 1/r region to a Keplerian inner disc. However, in one set of observations, the observed position-velocity map of cyclic-C3H2, together with a certain ballistic maximum velocity relation suggests that the radial shock coincides with a ballistic centrifugal barrier, which places the shock at rshock = 0.5rc, i.e. inward of rc, rather than outward as given by our simulations. It is argued that radial velocity plots from previous magnetic rotating-collapse simulations also indicate that the radial shock is located outward of rc. The discrepancy with observations is analysed and discussed, but remains unresolved.

Structure and kinematics of the Milky Way galaxy using atomic hydrogen

The present study uses the hyper-fine transition of atomic hydrogen, HI (1420 MHz) to map the structure and kinematics of the Milky Way galaxy. The observation was carried out for galactic longitude 20° ≤ ℓ ≤ 220° and galactic latitude −20° ≤ b ≤ 20° each in 5° steps using the SALSA 2.3m Radio Telescope located at Onsala Space Observatory, Sweden. The velocity components of HI clouds were determined using Gaussian decomposition of the observed spectrum and these values were projected onto the Galactic plane for the identification of spiral structure of the galaxy. The Perseus, Local and Outer arms were identified using the Longitude velocity plots and x-y plots (face-on maps). The rotational velocities of the HI clouds were determined using the tangent-point method and the resulting rotation curve comes out to be consistent with the literature in the range 4 ≤ R ≤ 8 kpc.

Design of a gust generator and comparison of model wind turbine and porous disc wake flows in a transverse gust

This paper outlines the similarities and differences between the wake characteristics of a porous disc and model wind turbine under transverse gust loading which is generated via a two-vane wind tunnel gust generator. Phase-locked two-dimensional two-component (2D2C) particle image velocimetry (PIV) measurements show that the capability of a porous disc in representing a wind turbine increases under gust loading. Compared to the uniform inflow case, normalized streamwise velocity plots of the porous disc and model turbine are in a better agreement under gusty inflow condition particularly in the near wake region. Comparison of the wake centerlines reveals a similar wavy wake pattern with no significant phase lag suggesting that the gust dynamics is the dominant factor in the determination of the wake dynamics.

Analytical solution for potential flow across two circular cylinders using the BIE in conjunction with degenerate kernels of bipolar coordinates

In this paper, we employ the bipolar degenerate-kernel in the boundary integral equation (BIE) to derive the analytical solution of potential flow across two identical circular cylinders. Analytical results are compared with those in Lebedev et al.. Discussions of the difference between our results and Lebedev’s solution are addressed. Velocity distribution is also plotted. Both analytical solution and velocity plots are given. The key tool is using the degenerate kernel instead of the closed-form fundamental solution. A closed-form fundamental solution is expressed in terms of degenerate kernel by using the bipolar coordinates for a case of two cylinders. The orientation, or so called the angle of attack is considered. The result shows that the degenerate-kernel approach can be an alternative tool for analytically solving some boundary value problems, although the complex variables is always employed. The extension to 3-D problems is promising and straightforward once the degenerate kernel is available since complex variable may have difficulty.

Entropy generation and natural convection on a cubic cavity with a pair of heat source at different configurations

Entropy generation and natural convection in a discretely heated cubic air-filled cavity has been numerically investigated in this study. A pair of discrete heat sources located at the bottom wall is at first considered for three different configurations. Both side walls are fixed at ambient condition, while the remaining walls are kept insulated. The three-dimensional, time-dependent continuity, momentum and thermal energy equations are selected as the governing equations of the present analysis. Galerkin finite element method is employed to solve those equations in non-dimensional forms. Parametric investigation is carried out by varying Rayleigh number within the range of 103–106 at fixed Prandtl number of 0.71. Results are presented in terms of qualitative plots of 3D velocity and thermal fields, and the quantitative evaluation of average Nusselt number and total entropy generation. A functional dependence of Nusselt number on the Rayleigh number and the distance between the symmetrically positioned heaters has also been presented in terms of empirical correlation. This comparative study shows that the configuration of the heaters has a great impact on the thermal characteristics, and thus provides one the opportunity to obtain an optimum arrangement for the system.

ANA LYSIS OF THE FLOW AND THERMAL FIELDS IN BOBTAIL ROOFS HEATED FROM THE BASE WALL

Analysis of airflow and thermal characteristics of attics of bobtail-shaped pitched roofs heated through a horizontally suspended ceiling is numerically carried out in this study. Pitch angles of 14o, 18o, 30o, and 45o within the standard pitch roof range are selected. The configuration falls within Rayleigh number 3.19 x 105  Ra  2.04 x 107. A finite-volume CFD code was used to solve the mass, momentum, and energy conservation equations governing the problem. The results obtained indicate a strong influence on the shape and angle of the roof. At lower roof pitches, the flow field is characterized by multiple counter-rotating vortices asymmetrically arranged within the enclosures. Eight cells in the 14o enclosure were reduced to five in the 45o roof pitch. The size and rotating strength of a vortex increase from the left corner to the middle of the enclosures. At higher pitch angles, the vertical wall obstructed the flow leading to a number of distorted cells. The maximum velocity within the aerodynamic boundary layer along the base wall occurs at Y=0.02 with the values U=0.013 and U=0.028 in the 14o and 45o enclosures respectively. The thermal field portrays a convection system of rising hot plumes from the base wall and descending cold jets from the inclined walls; all enclosed by thin boundary layers along the walls. Graphical plots of velocity and temperature variations along some cross-sections within the enclosures enable the prediction of some important heat and flow parameters.&#x0D;

Aerodynamic Performance and Wake Flow of Crosswind Kite Power Systems

This paper presents some results from a computational fluid dynamics (CFD) model of a multi-megawatt crosswind kite spinning on a circular path in a straight downwind configuration. The unsteady Reynolds averaged Navier-Stokes equations closed by the k−ω SST turbulence model are solved in the three-dimensional space using ANSYS Fluent. The flow behaviour is examined at the rotation plane, and the overall (or global) induction factor is obtained by getting the weighted average of induction factors on multiple annuli over the swept area. The wake flow behaviour is also discussed in some details using velocity and pressure contour plots. In addition to the CFD model, an analytical model for calculating the average flow velocity and radii of the annular wake downstream of the kite is developed. The model is formulated based on the widely-used Jensen’s model which was developed for conventional wind turbines, and thus has a simple form. Expressions for the dimensionless wake flow velocity and wake radii are obtained by assuming self-similarity of flow velocity and linear wake expansion. Comparisons are made between numerical results from the analytical model and those from the CFD simulation. The level of agreement was found to be reasonably good. Such computational and analytical models are indispensable for kite farm layout design and optimization, where aerodynamic interactions between kites should be considered.

Analysis of a Hypothetical Complete Loss-of-Coolant Accident in a Typical Research Reactor

In the present study, an analysis of a hypothetical complete loss-of-coolant accident in a typical open-pool research reactor is conducted. The reactor core is assumed to be completely uncovered and exposed to the ambient air. The possibility of passively cooling the decay heat of the exposed reactor core by natural convection to air and thermal radiation until core reflooding is investigated. A three-dimensional computational fluid dynamics analysis is conducted for the uncovered core while cooled by air natural convection and thermal radiation. The reactor core is simulated as a porous zone with decay heat generation specified as a cosine-shape distribution. The reactor core decay heat acts as a driving force for the coolant flow from the cold leg to the hot leg. The thermal equilibrium porous media model is used to represent the energy equation inside the core region. This study is conducted for core uncover time (the time interval between reactor shutdown and the moment when the reactor core is drained of water) of 10E3, 10E4, 10E5, 10E6, 10E7, and 10E8 s. Contour plots of temperature, velocity, density, and pressure at different values of core uncover time are illustrated. It’s found that for core uncover times of 10E3, and 10E4 s, the maximum core temperature exceeds the cladding melting point. The core maximum temperature is well below the melting point for uncover times of 10E5, 10E6, 10E7, and 10E8 s.

Superior Peroxidase-Like Activity of Gold Nanorattles in Ultrasensitive H2 O2 Sensing and Antioxidant Screening.

Nanozymes are artificial enzyme systems which are easy to produce, highly stable and cost-effective in comparison to natural enzymes. Herein, we evaluated the peroxidase-like activity of gold nanorattles (Au NRTs) having a solid gold octahedron core and thin, porous cubic gold shell. We also prepared solid gold nanocubes and nanospheres of similar sizes and surface charge as that of Au NRTs and compared their activity with standard horse radish peroxidase (HRP). All the prepared nanostructures followed Michaelis-Menten kinetics as observed from their substrate concentration vs. initial reaction velocity plot using 3,3',5,5'-tetramethylbenzidine (TMB) as a substrate. The kinetic parameters and the catalytic efficiency for the peroxidase-like activity of the nanostructures and HRP were calculated, and it was observed that Au NRTs possess the best nanozymatic activity with lowest KM and highest catalytic efficiency (kcat /KM ). The better activity of Au NRTs compared with other nanostructures and HRP could be attributed to the hollow porous structure with a solid core where different surfaces are available for reaction. Au NRTs, being the best amongst the tested nanozymes were further used for the sensing of hydrogen peroxide (H2 O2 ) and were found to sense H2 O2 down to 0.5 μM. Further, two naturally occurring antioxidants, tannic acid and ascorbic acid showed inhibitory effect on the peroxidase-like activity of Au NRTs in a concentration dependent manner which can be further used for screening of antioxidants or for determining the antioxidant potential.