Acoustic doppler velocimetry (ADV) is a common measurement technique for flow field in open-channel flows. Since ADV is an intrusive measurement method, the presence of ADV probe may causes changes in flow structure and may intensify the turbulence in sampling volume which can affect the experimental results and analysis. To explore these effects, in this study, particle image velocimetry (PIV) was employed to measure the flow field with and without the presence of a side looking ADV probe in a compound channel. The results of this research showed that the intrusion of ADV in the flow field increases the streamwise velocity in the ADV measurement volume by 1.7%. The more enhanced effect is also notified in the secondary currents so that in the present test conditions, the presence of the side looking ADV causes a decrease in lateral velocity by 4.5 times and causes an increase in vertical velocity by 2.7 times. Investigation of the turbulent intensities showed that the presence of the side looking ADV causes an increment in streamwise turbulent intensity, while does not significantly affect the lateral and vertical components. Furthermore, examining vertical Reynolds shear stress measurement data with or without the presence of ADV showed that the measured values differ in the two states and the presence of ADV decreases 30% of Reynolds shear stress in place of the control volume.

This paper presents the results of an experimental and numerical study of fully developed flow in a straight rectangular open channel over rough beds. Conical ribs were placed on the flume bottom to simulate different bed roughness conditions. Acoustic Doppler Velocimetry (ADV) measurements were made to obtain the velocity components profiles as well as the Reynolds stress profiles, at various locations. The experimental results are validated by simulations using an algebraic stress model. These investigations could be useful for researches in the field of sediment transport, bank protection, etc.

Acoustic Doppler velocimetry (ADV) is one of the most suitable devices for measuring flow characteristics. Determination of measurement frequency and duration, in a way that the results are calculated with the lowest error, is very important. The goal of this study was to determine the optimum measurement frequency and duration to save money and time. 3D instantaneous subcritical flocharacteristicsts are measured at 200, 100, 25, and 5Hz frequencies for a duration of 3 minutes, in a laboratory flume with an aspect ratio of less than 5. Then, 3D averaged velocities, shear velocity, turbulence intensity, and Reynolds shear stress are calculated. Results show that the reduction of error is independent of the number of measured data and its dependence is on the data collection duration and frequency. For measurements of 3D averaged velocity components, the appropriate measurement frequency and duration are 1Hz and 50 seconds, respectively. To determine the shear velocity, using logarithmic law, reducing the frequency and duration, results in a maximum error of 13%. For calculation of turbulence flow characteristics, like turbulence intensity and Reynolds shear stress, the measurement frequency, and duration of up to 25Hz and 50-70sec, respectively, results in an error of less than 10%.

One of the usual and useful techniques for the flow field measurement in open channels is Acoustic Doppler Velocimeter (ADV). Physical presence of ADV probe and its holding system against flow disturb natural flow pattern which can change turbulent flow structure. Thus, the error of the Acoustic Doppler Velocimeter is consist of its intrinsic error and the physical presence of ADV against flow. To study this issue in this paper, flow field in an open-channel is measured using Particle Image Velocimetry (PIV) technique and side-looking ADV probe. The results show that sreamwise velocity obtained from both methods are in good agreement and on average, there is 5 percent difference, while vertical and lateral components of velocity are considerably different. Also, comparison of sreamwise and lateral turbulence intensities and the Reynolds shear stress shows lower differences for measured points near the water surface and the differences increase approaching to the bed.

Introduction: To evaluate the role of Doppler waveforms of the uterine vessels in predicting preterm labor.Materials and Methods: This was a retrospective analysis of the uterine artery Doppler findings of 28 15-25 week singleton pregnancies with a spontaneous preterm labor were compared to 326 pregnancies delivered at term. 354 women who presented to our medical center from April 20, 2008 to November 20, 2008 were enrolled in the study. Pulsed-wave Doppler measurements were made of the maternal uterine arteries. These women were followed up until delivery.Results: The uterine artery mean resistance index (RI) was 0.76 and 0.66 in the preterm and term delivery groups, respectively (P<0.05). Bilateral diastolic notches were present in 41% of the preterm deliveries and 27% of the controls (P<0.05). The mean pulsatility index (PI) was 1.40 and 1.83 (46%) in the term and preterm delivery groups, respectively (P<0.05).Conclusion: Doppler of the uterine vessels could prove to be a good predictor of preterm labor.

This research presents recent advances on morphodynamic modeling over gravel dunes. Experiments were carried out on flow over 4 different dunes developed in 12m flume at Institute of Hydraulic Engineering and Water Resource Management of Technical University of Graz, Austria. Dunes are developed in the height of 4,6 and 8 cm and in wavelength of 1m with 2 different particle sizes (6 and 13 mm) and also two different lee angles (38 and 8 degree). The separation of flow over gravel fixed dunes is investigated by Acoustic Doppler Velocimetry (ADV) and Particle Image Velocimetry (PIV) and to compare the experimental results with numerical models over dunes, the 3D numerical model (SSIIM) is applied in this study. The results show that for the same two dunes under the same velocity but different flow depths, larger separation occurs under lower flow depths and a decrease in dune height causes a reduction in length of separation. Moreover the separation zone has a strong relation with lee angle and in the situation of low lee angle no flow separation was detected. Finally the result reveal that numerical model successfully simulate flow over dune in compared with ADV and PIV data. Although ADV application near the bed indicates probably weak performance for high discharge and low water depth of dune No.4, PIV results present more agreement with the numerical model in this region.