Nozzle numerical problems. Critical Pressure Ratio : .
Nozzle numerical problems In particular, many of the problems that appear to approximate numerically solutions of non-homogeneous conservation laws when the system admits stationary solutions are a consequence of the inability of the schemes to compensate the difference of the fluxes with the source terms nozzles in engineering practice, it is important to determine their cavitation characteristics, such a cavitation number and loss coefficient of the nozzle. Jan 1, 2021 · The nozzle's generic formula was manually calculated in the convergent nozzle flow phase and analyzed by the ANSYS flux program compared to the effects [20], [21]. The increased attention is due to a host of technological applications. Figure 14. youtube. assuming that the nozzle efficiency is 100% and initial velocity of steam is 50 m/s. This flow condition describes the presence of shock wave somewhere inside the nozzle. High performance engines in supersonic aircrafts generally incorporate some form of a convergent-divergent nozzle design using the Method of Characteristics Master’s Thesis 4. • The nozzle pressure ratio is P. The cross section of the nozzles may be circular, rectangu lar, elliptical or square. find the discharge velocity. 12. com/playlist?list=PLdoI Apr 23, 2019 · In this video solve numerical problem related to impulse turbine . 3,10Asanex-ample, Figs. , 2018]. 6. And, as shown in Fig. Nozzle angle will be assumed as 15˚ for impulse stage and 25˚ for reaction stages. This case is similar to case 5 except that the shock wave is precisely at the nozzle exit. A correctly designed convergent-divergent nozzle is always choked. 2. 28% to 84. be/UaoKRQuxd7wWatch Complete playlist of all the lectures on Thermodynamics (in series) by AK Aug 30, 2021 · In this video, I explained Numerical of Steam Nozzle. The head available at the nozzle is 400 m. The flow within the C-D nozzle (and the exit) is isentropic. 76ᵒ to 10ᵒ keeping all input parameters constant. How do we calculate the position of a normal shock in a converging-diverging (CD) nozzle? In this video, we will go through the necessary calculations in or Chapter 3 Nozzle Flow Supersonic Nozzle Flowfields: a Comparison of Fully Viscous and Navier-Stokes Solutions N. The paper presents initial steps in numerical analysis of flow, generated by convergent-divergent nozzle with Mach number M = 3. This paper presents a numerical simulation of the spray painting process using a pneumatic atomizer with the help of a computational fluid dynamics code. P2 /P 1=0. Discussions are made on the comparison between experimental and numerical results. • A valve attached to the nozzle exit is adjusted to vary back pressure. in a convergent nozzle, the cross sectional area decreases continuously from its entrance to exit. Various numerical tests presented in this study relate to the influence of the variation of the geometry of the nozzle such that the angle of divergence as well as the effect of the variation of the input of the characteristic quantities of the pressure flows. ) with Oct 1, 2020 · A numerical study has shown that by increasing the nozzle angle from 75⁰ to 90⁰ for a two jet turbine, the efficiency of the turbine increases from 76. 1 cm. Pilot-tube readings at inlet and exist of the nozzle ae 6. The problems involve calculating nozzle dimensions, mass flow rates, efficiencies, and other parameters given steam conditions at the nozzle inlet and exit. Mar 30, 2015 · The desire to more reliably predict the noise reduction available to individual jet nozzle design concepts has led to the introduction of large-eddy simulation (LES) techniques to jet noise problems, of course thanks to the enormous advances in computer power over the last 2–3 decades. Air is discharged from a C - D nozzle. 17 April - 23 April. Numerical output The results are presented for nozzle flow subsonic - supersonic. When the actual pressure ratio is larger than the critical pressure ratio, the nozzle is considered to be choked. And About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright In this video, I explained Numerical of Steady Flow Energy Equation For Nozzle. 46, and reduction in relative velocity while passing through the buckets as 15%. About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright Nov 27, 2021 · About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright In this video, I explained Numerical of Steam Nozzle. In this case, the separation of the flow from the nozzle wall can play a positive diverging nozzle, they highlighted that numerical results obtained by using the proposed system of model equations agree well with the experiments. More recently, the interaction of the two adjacent jets was studied in a six-jet Pelton turbine for eight operating points ranging from N/N BEP = 0. From the code independently was checked with the commercial computational fluid dynamics software. , author = {Vinko Martinis and Branimir Matijašević and Željko Tuković}, title = {A Numerical Solution to the Inverse Problem of Supersonic-Nozzle Design}, journal = {Strojniški vestnik - Journal of Mechanical Engineering}, volume = {48}, number = {4}, year = {2002}, keywords = {supersonic nozzle; nozzle design; numerical Subject - Fluid Mechanics 2Video Name - Numerical 1 Flow Through NozzleChapter - Flow Through NozzleFaculty - Prof. When the back pressure of a nozzle is above the design value, the nozzle over expands. com/Complete playlist of Th Aug 29, 2021 · In this video, I explained Numerical of Steam Nozzle. 2 bar and calculates the dryness fraction as 0. A numerical simulation of a C–D nozzle using ANSYS at the supersonic Mach number for a duct flow was studied [22]. 3) The second problem involves calculating pressures, temperatures, velocities and throat area given inlet conditions and an exit pressure, and determining the nozzle type. 0 m supplies water to a house. 6 and 7 compare experimental and Mar 31, 2019 · In this video derive an expression for critical pressure ratio in case of nozzle. K. The Mar 8, 2024 · The nozzle with a throat diameter of 6 mm in the numerical simulation is a 10-fold similarity enlargement of the entire 0. 8. A M Pradeep, Department of Aerospace, IIT Bombay. 14% [58]. The numerical simulations of compressible flow passing through a convergent-divergent (CD) nozzle with a fixed geometry are carried out. The considered duct length is L = 10D for a diameter ratio of 1. Hello everyonewelcome back we started doing, , going through the procedure of how to solve problem in as DynamicsG, 1D isentropic gas dynamics through a convergent divergent nozzle. Find the inlet and exit stagnation pressure, exit Mach numbers, exit flow velocity and nozzle Apr 27, 2020 · #RoyalMechLectures A nozzle operating at the maximum mass flow is said to be choked. Lecture 16: Boiler Trial; Lecture 17: Nozzles and Diffusers - Momentum and Continuity Equations ; Lecture 18: Nozzles and Diffusers- Efficiency and Critical Pressure ; Lecture 19: Nozzles and Diffusers- General Relationships and Supersaturated Flow; Lecture 20: Problem Solving (Nozzles 6. com/playlist?list=PLdoI Exit velocity of nozzle and Mass flow rate calculations. 10. intake and nozzle problems numerical - Free download as Word Doc (. The aim of the present work is to investigate the flow characteristics in a converging diverging nozzle with a wide range of inlet pressure. The numerical simulations carried for nozzle pressure ratio's (NPR) 3, 5, 7, 9 and 11. PROBLEM DESCRIPTION Oct 16, 2017 · Numerical simulations were conducted for analyzing the multiphysics problem by coupling fluid, thermal and structural analyses of a rectangular convergentdivergent nozzle [Bhide et al. The convergent-divergent (CD) nozzle geometry has been modeled and simulated employing K-ε turbulence model for standard wall function. instamojo. • Solve numerical problems for a Pelton Wheels and a Francis The theoretical velocity issuing from the nozzle is given by v1= (2gH) 1/2 or v 1= (2p/ρ) 1/2 solve problems. The nozzle converts the low velocity, high pressure, high temperature gas in the combustion chamber into high velocity gas of lower pressure and low temperature. Feb 10, 2021 · The ejector nozzle flowfield was solved on an unstructured grid using the unstructured grid solver in Wind-US 3. Oct 1, 2019 · These problems are mostly related to the overexpanded flow regime in the nozzle [1, 2], when in a large part of the nozzle contour the static pressure is less than the ambient pressure, thereby the negative contribution in the thrust of the nozzle is realized. The pressure just downstream of the shock wave equals the back pressure since the flow is subsonic there. It gives the key parameters and equations for calculating inlet and exit angles, velocities, work done, power, thrust, and efficiency. Jul 9, 2016 · A numerical simulation study was performed to examine the effect of nozzle geometry and divergent length on gas-particle flows in dual hose dry ice blasting. 95 × 105 N/m 2 and 5. The document contains 15 problems involving the design and analysis of convergent-divergent nozzles used in steam turbines. 139. Results In this video, I explained Numerical of Steam Turbine. The proposed numerical technique solves two-dimensional Dec 1, 2017 · By using the methodology proposed by Marchi and Maliska [13], the numerical code provides results for all flow regimes into the rocket engine nozzle (sub-, trans- and supersonic ones), unlike the commonly used method of characteristics [15], [16], which can be used only for hyperbolic problems (correspondent to supersonic flows). Jan 1, 2015 · Conclusions 269 Jin Hyeon Kim et al. When the backpressure of a nozzle is below the designed value of pressure at exit of nozzle, the nozzle is said to be _ Sep 25, 2023 · CFD is a branch of Fluid Mechanics which rely on numerical methods and algorithms to solve and analyze problem that involves fluid flow. To solve this problem, we consider a streamline that leads from the water surface to the outlet of the nozzle. The second example gives conditions of 5 bar steam expanding to 0. 6 mm nozzle shape. May 1, 2022 · Several numerical works are present in the literature, aiming to simulate the flow field into the mould. • The nozzle exit conditions will be Apr 1, 2015 · Flow separation in supersonic nozzles is a basic fluid-dynamics phenomenon that occurs at a certain range of pressure ratios, resulting in shock formation and shock/turbulent-boundary layer interaction inside the nozzle. Lalit KumarUpskill and get Placements wit Explanation: In case of a convergent nozzle, when the flow is choked the exit Mach number is 1. 2, the only difference between the conical nozzle and swirling impeller nozzle is that the swirling impeller nozzle has an impeller. 24 April - 30 April Problems: 1. 97, speed ratio as 0. Fig. May 2, 2020 · About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright The document provides three examples of dry saturated steam expanding isentropically through a nozzle. Dec 1, 2022 · Many studies have been developed to investigate the influence of nozzle end-wall clearance leakage flow on the VNT performance. a =4. A steam nozzle is a duct or passage of smoothly varying cross sectional area which converts heat energy of steam into kinetic energy . It is used in a case where the back pressure is equal to or greater than the critical pressure ratio. Velocity, pressure, and Mach number contours are computed for every nozzle configuration obtained. 1. 3 in Ref [1], as Mar 1, 2024 · The conical nozzle structure and the swirling impeller nozzle structure in the numerical simulation are the same as the structures applied in AWJ rock breaking experiments. The nozzle project 20 mm on outside & 30 mm on inside of shell. 5 × 10 5 N/m 2. Recently, extensive studies have been devoted to understand the fluid dynamics phenomena in rocket motor nozzles. 2 bar. 1. Topics: ThermodynamicsFor Handwritten Notes: https://mkstutorials. Sample problems are worked through step-by-step showing calculations for impulse turbine performance parameters like blade angles, relative velocities, forces, power, and GATE Exam. [8] studied the effect of the guide vane leakage flow on the flow field downstream of the nozzle vane with the large and small openings through both experimental and numerical methods. May 1, 2024 · In this case, for the conventional diesel nozzle with symmetrically arranged holes, the hole on the side far away from the methanol nozzle cannot fulfill the ignition effect, thereby causing the problems of reducing effective ignition energy, prolonging methanol combustion duration and reducing burn efficiency, which will seriously affect the • The nozzle is connected to a tank supplying the inlet station with fixed total pressure and temperature. A cylindrical water tower of diameter 3. The document provides examples of problems involving impulse steam turbines. Hideaki Tamaki et al. 08 bar • The critical pressure ratio is • Therefore the nozzle is choking. The bucket velocity is limited to 300 m/s and the average nozzle efficiency is expected to be 95 %,expect for a 2-row Curtis stage for which it will be 90%. The third example C-D Nozzle Numerical Example, Multiple Choking Points . Simulating the solution for convergence… remain attached on a concave plug nozzle with a constant radius cowl; for a detailed numerical study of flow separation phenomena of plug nozzles see Ref [6]. Najjar et al. In order to check if the nozzle is operating at choking conditions, we compare the actual pressure ratio to the critical pressure ratio. 16) IsentropicFlow d cm V m s t Given T C P A typical convergent nozzle is shown in fig. Here, the process is adiabatic compression. com/playlist?list=PLbkIghv Example # 10. Chapter: Steam TurbinePlaylist of Steam Turbine: https://www. Non-dimensionalizing the Governing flow equations and setting them up with relevant initial and boundary conditions and solving using the Maccormacks technique. The objective was to validate the unstructured solver for the ejector nozzle flow. The droplet characteristics that are necessary for the droplet trajectory calculation were experimentally investigated using different shaping air flow rates. The level of water in the water tower is 35 m above the point where the water enters the house through a pipe that has an inside diameter 5. com/playlist?list=PLdoI BY BS In this video ,explanation has been given regarding how to find the Velocity of Steam ,cross sectional Area at throat and discharge(mass flow rate). Jan 1, 2021 · Numerical analysis is performed on a dual bell nozzle designed for an experimental semi-cryogenic rocket engine application to predict the effect of film injection on nozzle flow characteristics Typical Conical Nozzle Contour Credit: Georgia Tech D t = Throat diameter R 1 = Radius of curvature of nozzle contraction N = Transition point from circular contraction to conical nozzle L N = Nozzle Length D e = Exit diameter • R 1 ~ 0. Inverted conics and tangency enforcing plug-crown blending operations should be considered only with inward turning cowls, seen in Fig. The flow everywhere within the C-D nozzle is isentropic except right at the exit. The critical pressure ratio for initially super-heated steam is _ as compared to initially dry saturated steam. At what speed does the water come out of the nozzle when the water surface is at the height h above the nozzle opening? Figure: Discharge of water from a hose. Lect-34 • Primary nozzle: we first check for choking of the nozzle. and hot-” ring tests of overexpanding nozzles. 31 – Perfect nozzle is too long • Optimum nozzle (Bell shaped nozzles) – Balance length/weight with the 3D flow losses • Plug nozzle and Aerospike nozzle – Good performance over a wide range of back pressures Other Nozzle Design Issues Karabeyoglu 12 ( ) ( ) T m u e + P e − P a A e + = 2 1 cos α! α: Nozzle Cone Angle Feb 1, 2024 · The significance of three-dimensional numerical simulation lies in providing a crucial methodology for multiple lateral nozzle design, thereby ensuring the viability and efficacy of the novel configuration. / Procedia Engineering 105 ( 2015 ) 264 – 269 In this study, a numerical analysis has been performed by changing the pressure, nozzle diameter and jet angle of the sub nozzle in order to visualize the flow in an air jet loom. Assume that the nozzle of the tyre is blocked and you push the pump to a volume 1/4 of V. 39 at nozzle exit. It was found that the droplet size distribution depends on both the atomizing and Jun 20, 2020 · The flow is incompressible and inviscid. Area Ratio in a Laval Nozzle: 10. The mass flow rate through sonic nozzles is typically expressed dimensionlessly by the discharge coefficient C D, as described by the ratio of the actual mass flow rate to the mass flow rate under ideal conditions (one-dimensional, isentropic flow of a distributions along the nozzle’s centerline of pressure, axial velocity and Reynolds stress; (b) profiles along radial cuts at different positions of the nozzle of axial velocity, radial velocity, shear stress and Reynolds stress; (c) wall distribution pressure and Wall Shear Stress (WSS); and (d) jet width along the centerline. 18. 89 to N/N BEP = 1. Jul 20, 2022 · Example \(\PageIndex{2}\): Water Pressure. Aug 28, 2021 · In this video, I explained Numerical of Steam Nozzle. Nov 1, 2021 · Fig. UNIT III STEAM NOZZLES AND TURBINES Flow of steam through nozzles, shapes of nozzles, effect of friction, critical pressure ratio,supersaturated flow and reaction principles, compounding, velocity diagrams for simple and multistage turbines, speed regulations-governors and nozzle governors. Mass Flow Rate Through a Laval Nozzle: 11. Bhaskar Roy, Prof. 37 4. The total number of meshes is 1,451,144. Hence discontinuity flow phenomena appear in this flow problem. The first example gives the conditions of 5 bar steam expanding to 1 bar with a dryness fraction of 0. 13 March - 19 March. 577 9. The critical pressure ratio initially dry saturated steamis. 10 (d) shows the numerical simulation results of the nozzle clog height is higher than the measurement results; however, the trend of the nozzle clogs heights is the The aerodynamic design of classical and innovative nozzle concepts is investigated by an inverse method. [12] investigated the effect of nozzle design on the jet characteristics and the flow field in the mould using a finite element methodology and the k-ε turbulence model. 20 March - 26 March. The document contains several problems related to impulse turbines. Performances of two numerical methods which are used in the present study of unsteady flow problem are also discussed and indications for future development of numerical tools to study nozzle problems are Jul 9, 2022 · A nozzle of 300 mm inside Diameter & 12mm thickness is to be provided in the shell. It asks the reader to calculate various parameters such as blade angles, power developed, axial thrust, and diagram efficiency given information about the steam conditions, nozzle angles, blade speeds, and other specifications. CFD analysis has been conducted to analyze flow pattern of Why should I learn to solve Mechanical Engineering questions and answers section on "Steam Nozzles and Turbines"? Learn and practise solving Mechanical Engineering questions and answers section on "Steam Nozzles and Turbines" to enhance your skills so that you can clear interviews, competitive examinations, and various entrance tests (CAT, GATE, GRE, MAT, bank exams, railway exams, etc. Mitra and M. Solution: Problem # 2. A convergent-divergent nozzle is used if the nozzle pressure ratio is high. Ramjets and rockets typically use a fixed convergent section followed by a fixed divergent section for the design of the nozzle. A 137 mm diameter jet of water issuing from a nozzle impinges on the buckets of a Pelton wheel and jet is deflected through an angle of 165oby the buckets. . 27 March - 2 April. Chapter: Thermal Power PlantPlaylist of Thermal Power Plant: https://www. Prof. The second flow problem relates to the problem of supersonic inflow and subsonic outflow. com/playlist?list=PLdoIhVhbPQV6gIv May 13, 2021 · A nozzle is a relatively simple device, just a specially shaped tube through which hot gases flow. • Except for two special conditions which we will discuss later, the nozzle exit pressure will always be equal to the back pressure. In case we are unable to obtain cavitation characteristics of the nozzle experimentally, there is the possibility to conduct numerical simulations of the flow in the Venturi nozzle. 10 (d) shows that when the minimum mesh heights were 1 mm, 2 mm, and 3 mm, there was no significant difference in the distribution of the nozzle clog on the nozzle wall. 10 April - 16 April. Basically, the physical problem encountered in nozzle flows is essentially the result of boundary-layer separation caused by Feb 28, 2018 · I hereby explain the step-by-step procedure to solve problem based on Convergent and Divergent Nozzle in Tamil. 33 Pressure in the nozzle of this fire hose is less than at ground level for two reasons: The water has to go uphill to get to the nozzle, and speed increases in the nozzle. 7. 08/1=4. the discharge pressure is 1. The first problem involves calculating mach numbers and flow rates given inlet conditions. 94, and calculates the exit velocity as 644. 82 × 10 5 N/m 2 respectively. Assuming no losses due to shock at inlet, calculate for a mass flow of 1 kg/sand symmetrical blading (i) blade inlet angle (ii) driving force on the wheel (iii) axial Jul 1, 2011 · The numerical solution of turbulent compressible flows in nozzles is a challenge problem in fluid dynamics applications. The blade velocity is 350 m/s and the blade velocity coefficient is 0. When the back pressure of a nozzle, Pb, is below the design value, the nozzle under expands. About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket May 23, 2020 · In this video solve Numerical problem related to pelton wheel turbine NUMERICAL PROBLEMS. Sep 9, 2017 · Get complete concept after watching this video. A convergent divergent adiabatic steam nozzle is supplied with steam at 10 bar and 250°c. Mar 22, 2017 · Numerical are solved using Mollier diagramIf like this video please donate PAYTM 9422112581 UPI "9422112581@UPI" The velocity of steam, leaving the nozzle of an impulse turbine is 1000 m/s and the nozzle angle is 20o. Divergent Nozzle: Solved Problems: 1. Fiebig STATEMENT OF PROBLEM The conventional method for the analysis of supersonic nozzle flowfields is to assume the flow to be inviscid everywhere except near the wall where a thin viscous layer grows. The shape of the nozzle is designed such that it will perform this conversion of energy with minimum loss . Welds joint efficiency for shell as well as nozzle is 85% while corrosion allowance is 2 mm. 2. Calculate the final temperature of air in the pump? (For air , since the nozzle is blocked air will not flow into tyre and it can be treated as an adiabatic compression). 1:Calculating the throat and exit cross-sectional areas for convergent-divergent nozzle Feb 23, 2019 · About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features NFL Sunday Ticket Press Copyright The starting process of two-dimensional nozzle flow is investigated both experimentally and numerically. Solution. 9 Various numerical simulations of ‘ ow problems featuring ‘ ow separation have shown that the numerical prediction of ‘ ow separation with state-of-the-art turbulence modeling re-sults in good agreement with experimental data. In spite of its lowered pressure, the water can exert a large force on anything it strikes by virtue of its kinetic energy. . = = = = = = = = = = = = = = = = = = = = = = Chapter: First Law of Thermodyna Jan 12, 2023 · steam nozzle numericals || steam nozzle problems || numerical on steam nozzle👇👇👇 thernal engineering playlist- https://youtube. Mar 20, 2021 · PROBLEM A Steam turbine is to operate between 150 bar, 600˚C to 0. 84. Critical Pressure Ratio : Problem (12. Numerical output for Mach 3 and 10 characteristic lines. 75D t is typical e--> expansion ratio (A exit/A*) θ nozzle R 1 X N Y N θ nozzle R 1 Y X θ nozzle D t R 1 N L Abstract : Set up of a time marching, finite difference solution for the Quasi 1D subsonic supersonic nozzle flow. This nozzle configuration is called a convergent-divergent, or CD, nozzle. Optimization of channel inlet geometry and nozzle distribution contributes to substantial reductions in peak Stanton number and wall pressure. The inlet stagnation . 3 April - 9 April. Results of verification and methodical analysis of this acoustic methodology are presented. Variation in divergent angle is made from 4. 10 bar. 05 /P. Find: Dec 8, 2021 · Link of Lecture-55 (Steady Flow Energy Equation):https://youtu. Numerical Problems. Jul 1, 2021 · Special attention requires the numerical treatment when non-homogeneous hyperbolic systems admit steady solutions. Aug 1, 2000 · Related Records ID Relation Title 20010061390 Work Analytical Solutions to the Unsteady Response of an Isolated Finite Span Swept Airfoil to an Incident Gust and Unsteady Response of a Rectilinear Swept Cascade to an Incident Gust Problems 20010061406 Work A Low Order and a High Order Solution for a Converging-Diverging Nozzle Problem 20010061422 Work Generation and Radiation of Acoustic Waves Lecture 15: Combustion of Fuel (Problem Solving) Unit-4. Dec 26, 2024 · Sonic nozzles are a widely used state-of-the-art secondary gas flow standard [1] that is operated according to the principle of flow throttling. assuming coefficient of velocity as 0. pdf) or read online for free. Less. The convergent-divergent nozzles with varying cross-sections are designed and are investigated by numerical simulations. The input and output files and comparisons of the velocity and total temperature profiles can be found on the Unstructured Ejector Nozzle page. To accurately determine Q mass_actual in the numerical simulations, we must capture the rapid changes in flow velocity near the nozzle wall. The implementation of these nine numerical schemes to case of isentropic flow show all scheme work well. I discussed how to solve when it is simple case of isentropic subsonic Sep 21, 2023 · Nozzle flow properties and its numerical problems @article{. temp 250 o C and exit static pressure, 1. II. doc), PDF File (. stores. May 1, 2010 · Numerical methodology for the simulation of nozzle acoustic performance is described in detail, including methods for simulation of near and far field of a nozzle, for generation of input perturbations and for the processing the far-field noise. 3 m/s.
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