Title: Practical Method for Validation of Velocities Measurements in Water and Wastewater Using Acoustic Doppler Velocimeter (Micro-ADV)

Transcription

1 Editorial Manager(tm) for IWA Conferces Manuscript raft Manuscript Number: IWA-84R Title: Practical Method for Validation of Velocities Measuremts in Water and Wastewater Using Acoustic oppler Velocimeter (Micro-AV) Article Type: Full Paper (accepted at conferce) Corresponding Author: Professor Rodrigo Braga Moruzzi, Ph. Corresponding Author's Institution: State University of São Paulo First Author: Rodrigo Braga Moruzzi, Ph. Order of Authors: Rodrigo Braga Moruzzi, Ph. Manuscript Region of Origin: BRAZIL

2 Manuscript Click here to download Manuscript: IWAMex_29_Full_paper_Track2_Topic_Moruzzi_Reali_Brazil.doc Practical Method for Validation of Velocities Measuremts in Water and Wastewater Using Acoustic oppler Velocimeter (Micro-AV) Rodrigo Braga Moruzzi, Marco Antonio Palva Reali 2 Institute of Geoscices and Exact Scices (IGCE) State University of São Paulo (UNESP). Avida 24 A, 36-9 Rio Claro SP -Brazil. Tel.: rmoruzzi@rc.unesp.br 2 epartmt of Hydraulics and Sanitary Engineering, School of Engineering in São Carlos, University of São Paulo (EESC-USP). Av. Trabalhador Sãocarlse, 4 Ctro São Carlos- SP, Brasil Tel , mapreali@sc,usp.br 2. Key words: validation; Micro-AV; velocity measuremts Abstract This article prests a practical method to validate velocities measuremts in water and wastewater using Micro-AV device. The amount of scattering particles and air can interfere in acoustic measuremts. A pdulum text for air interferce evaluation was applied on top of the proposed sonorous texts for the manufacture. For this, several air conctrations were investigated (from to mg of air. min - ). The set parameter sample frequcy was verified. According to the results, it was possible to verify that the method was appropriated to evaluate the AV application and that the Micro-AV ultrasound could be applied to measure velocities on x- direction. However, the same method must be applied in y and z-directions in order to verify the air interferce on velocities measuremts. Introduction and objectives The hydrodynamic performance in sanitary gineering projects is a very important issue and it is one of the most common causes for inefficicy of several plants. The acoustic oppler velocimeter (AV) is a powerful tool for velocity measuremts in water and wastewater treatmt plants and the use of it can help operators to assess hydrodynamic problems on working units. The amount of particles and air in water can modify the acoustic sign, used to Acoustic oppler Velocimeter (AV) velocity measuremts. Thus, a diagnostic must be run to verify all aspects of system performance. The more particles the better because of their work as a scattering materials for acoustic wave propagation. On the other hand, air bubbles can modify the speed of sound, interfering on oppler shift to velocity. The delay sign extsion is not mtioned on AV manual but it certainly depds on bubbles size and conctration in water. Lundh, Jönsson and ahlquist (2) proposed a pdulum essay for dissolved air flotation tanks analysis and the results indicate a reduction up to % in high conctration bubbly water velocity measuremts, comparing to clear water using Acoustic oppler Velocimeter (AV). However, the proposed method was not detailed and the resultant vector was analyzed as a whole instead of each direction one by one.

3 This paper prests a detailed pdulum method considering that interest velocities measuremts may be in any of three directions (x, y and z) and that each application demands a particular analysis. In this paper only the top x-axis velocities measuremts were analyzed. In these situations, the pdulum was in the minimum track position. The aim of this paper is to propose a new way to verify AV limitation based on the pdulum essay. Additionally, the frequcy sample of HZ was established based on the dimsionless value (F) proposed by García et al. (24). The AV validation detailed method for velocity measuremts constitutes an important tool before getting data and its use can assist water professionals to better understand flow conditions in any water delivery application. Methods The AV equipmt uses waves of sound of a particular frequcy aimed at attaining the three-dimsional componts of the fluid velocity according to the oppler principle. The signal gerated from the sder is reflected by particles in half portion of the liquid to the receivers and used to compute the oppler signal through which the componts of the velocity are calculated. Figure prests a photo and a scheme of the connecting rod sampling tip, illustrating the emitted signal, the control volume and the three receivers. The manufacturer states that the visualization of the flow is not necessary, as the methods that use the image, and suggests it as one of the advantages of the equipmt. However, the fluid must contain scattered material in a large ough amount to reflect the gerated signal to the receivers. The equipmt has software for data acquisition and a program that evaluates the signal s performance. The acquisition software allows setting sampling frequcies (fr) from to Hz. It is important to point out that the data collection frequcy (fs) is 6MHz and the relation betwe fr and fs is giv by: fr=fs/n, where N is the number of samples contained in the time /fr. The correct data frequcy sampling definition depds upon the flow conditions. 3º mm Vol. <, cm 3 Figure MicroAV photograph and illustrative scheme of the sampling probe tip. Source: Adapted to SonTek (24). Extracted from Moruzzi and Reali (29). Before collecting data, the diagnostic program was run in order to verify sign performance. Using the program, it is possible to verify if there is sufficit scattering material in water, among other parameters.

4 The Sample frequcy was established based on the dimsionless value (F) proposed by Garcia et al. (24). According to the authors, the Equation can be used to evaluate AV performance for turbult conditions. F=f r.l/uc () where, L is the eddy lgth scale; Uc is the convective velocity and f r is the user set frequcy. The authors describe that a good sampling criterion should consider values of F>2. In cases where this criterion cannot be satisfied (F<2), a set of curves are proposed to estimate the values of necessary corrections. The eddy lgth scale was measured trough image analyzes of several photos tak inside the tank and the convective velocity was calculated based on the area and flow. The velocity measuremts were verified by mean of several essays made to a pdulum. As proposed by Lundh, Jönsson and ahlquist (2), the pdulum was constructed to introduce a movemt, which made it possible to compare the velocity measuremts in clear and bubbly water, in differt air conctrations (Figure 2). The essays consist on starting the pdulum oscillatory movemt from the same position after air insufflation adjustmt. The results must be analyzed in terms of the peak of speed for each oscillatory movemt until the pdulum stops. In this way, several ranges of known velocities can be analyzed for differt air insufflations. For this purpose the top x-axis velocities measuremts were analyzed. In these situations, the pdulum was in the minimum track position indicating a perpdicular position to the theoretical movemt of bubbles. In this paper, the velocity measuremt interferce could be analyzed based on t induced pdulum oscillatory movemt in several air conctrations. The results were analyzed by statistical methods. N.A Water Level ºC Bubbly water a) b) Figure 2 a) Illustrative scheme of the pdulum apparatus, b) Photography of the probe tip in bubbly water.

5 Cumulative frequcy ( Nb/No) Results and discussions The analysis of images indicates that the eddy lgth scale (L) was around cm and the convective velocity (Uc) was around 3 cm.s -. So, the F parameter proposed by Garcia et. Al. (24) was much higher than (F=2) the minimum limit (F=2), indicating that the HZ sample frequcy was adequate for the essays conditions. Figure 3 prests the bubble size distribution for t air conctrations in terms of cumulative frequcies (Moruzzi and Reali 27). It can be observed that varied from around 8 to 9% wh altering AC from.3 to 2.2 g of air per m 3 of water. Regarding velocity interferces, Figure 4 shows the results for all investigated conditions. For all essays, the curves had the same behavior. Figure clearly indicated that bubbly and clear water had a certain range of variability. However, analyzing the average of essays for each air conctration, it was possible to verify that it did not have significant interferces in AV measuremts (Figure 6).,9,8,7 Cumulative frequcy of BS varying AC AC.3 AC.6 AC 2.2 g of air/m^3 of water,6,,4,3,2, <x<= <x<=2 2<x<=3 3<x<=4 4<x<= <x<=6 6<x<=7 7<x<=8 8<x<=9 Bubble size range (μm) 9<x<= <x<= <x<=2 Figure 3 Cumulative frequcies of bubbles in number by varying AC in terms of recirculation flow. BS results obtained by a non-intrusive image analysis method in a steady state pilot plant contact zone. Fixed parameters: HTcz 9 s, ph 6. P sat 4±kPa, θ 22±ºC, dp needle valve /8. Extracted from Moruzzi and Reali (27)

6 Velocidade na direção X (cm/min) -2 Tem Time(s) po ( K 6 J I G 2 es nt re ife 4 J 6 K 7 ção x (cm /m B g) /seg) -4 C 2 6 s io te I H G F J K 6 ) i g) po Time(s) (se K s J 4 m po Time(s) (s eg fe r Te m Te I 4 3 sa H 3 x (cm/m -2-4 G 2 B F direção -2 2 Velocida de di E 4 reção x (c m 2 ade na 4 in) d) Velocid c) I Te mp Time(s) o (se F H 3 os i sa C os ai E E s 4 seg ) H F B es 3 G -2-4 re nt 2 di fe C 2 de na dire 2 4 Velocida 4 in) b) a) er dif E s nte C sa B ios e Figure 4 Group of Results from pdulum essays for each investigated conditions. a) Without air insufflation s; b) 2mg of air. min. ; c) 2 mg of air. min. e, d) mg of air. min.. The prested values refer to velocities measuremts on the x-axis. a) b) - - -,,,,, 2, 2, 3, 3, 4, 4,,, 6, 6, 7, 7, 8, 8, -,,,,, 2, 2, 3, 3, 4, 4,,, 6, 6, 7, - 3, 2,7 2,8 2,8 2,9 2,9 3, 3, 3, 3, 3,2 3,2 3,3 3,3 3,4 3,4 3, 3, 3,6 3,6 3, 4, 4,, c) Range variability in velocity measuremts ind) Figure the same essays conditions for t pdulum essays: a) clear water b) bubbly water (mg air.min-) - - -,,,,, 2, 2, 3, 3, 4, 4,,, 6, 6, 7, 7, -,,,,, 2, 2, 3, 3, 4, 4,,, 6, 6, 7, 7, 3, 4, 4, 3, 4, 4,,

7 Velocity average with differt air conctration (cm.s - ) média dos picos de velocidade com bolhas (cm/seg) resultado saios complemtares com AV 2 mg of air. min. - 2 mg of air. min. - mg of air. min. - bolha l/min bolha 2l/min bolha 4l/min Velocity average with no air insufflations (cm.s - ) média dos picos de velocidade sem bolha (cm/seg) Figure 6 Top arithmetic medium velocities for a wide range of points considering air insufflations from to mg of air.min -. It is clear that the velocity intsities are similar wh comparing results from Figure 4. It is also clear that there were variations on the same essay condition as showed in Figure. Figure 6 was constructed by means of medium values for each air insufflation. The results pointed out a very similar behavior represted by mean of the coincidce of the results. Evidtly, the proposed essays must be run for the other axis evaluation but the prested methodology can constitute an important tool to validate AV application for a wide range of conditions. Once the AV is validated for a specific condition, it can be applied to evaluate hydrodynamic performance in water and wastewater treatmt plants, becoming a powerful tool to assess and to increase units efficicy. The statistical analyses indicate that the velocity values in x-direction were in accordance for a wide velocity measuremt range (Figure 7) for 9% of confidce. Results indicate that the pdulum essay along with the diagnostic software can assist the AV validation for several application, thus permitting operators to evaluate the hydrodynamics behavior of working treatmt plants units.

8 cm.s - No introduced air 2 mg air. min - 2 mg air. min - mg air. min - Figure 7 Box plot for air insufflation s from to mg of air.min - considering 9% of interval of confidce. Conclusions The sample frequcy of Hz based on the dimsionless F analysis was adequate for the AF studied conditions. The AV probe could be used for quantitative analysis considering the x-direction under the studies conditions. Referces GARCÍA, C.M.; CANTERO, M.I.; NIÑO, Y.; GARCÍA, M.H. (24). Acoustic oppler Velocimeters (AV) Performance Curves (APCs) sampling the flow turbulce. Acess in: 24 mar LUNH, M.; JÖNSSON, L.; AHLQUIST, J. (2)Experimtal studies of the fluid dynamics in the separation zone in dissolved air flotation. Wat. Res., v. 34, n., p MORUZZI, R.B; REALI, M.A.P. Characterization of Micro-bubble Size istribution in AF Contact Zone by a Non-intrusive Image Analysis System In: th International Conferce on Flotation in Water and Wastewater in Seoul (ROK) in September 27. MORUZZI, R.B; REALI, M.A.P. Software evelopmt for Hydrodynamic Study in Water and Wastewater Treatmt Systems. Holos Environmt. v. 9, nº, 29.