Taketoshi Okuno

A highly accurate iterative PIV technique using a gradient method

An iterative PIV technique in which the combination of the iterative cross-correlation technique and three-point Gaussian peak fitting for a sub-pixel analysis has been used can improve the spatial resolution and accuracy of measurement. It is reported that the root-mean-square (RMS) error of the technique is of the order of only 0.04 pixels. However, a large interrogation window, typically 32×32 pixels or larger, should be taken, resulting in a low resolution, in order to achieve the high sub-pixel accuracy. The high accuracy is not compatible with high spatial resolution. In this paper, a new high-resolution PIV technique based on a gradient method is proposed. Initially, the pixel unit displacement is detected by the iterative method. Then, the sub-pixel displacement is evaluated by the use of the gradient method instead of the three-point Gaussian peak fitting technique. The error of the proposed technique is analytically assessed by Monte Carlo simulations. The RMS error is of the order of 0.01 pixels even with a small interrogation window, for instance 13×13 pixels or less. Thus, the method can achieve high sub-pixel accuracy and high spatial resolution compatibility.

Image measurement of flow field using physics-based dynamic model

The PIV technique is generalized from the viewpoint of the identification problem of a flow field. The process of obtaining a velocity distribution as an image measurement can be considered as a parametrization problem of a dynamical system. In almost all conventional techniques, the velocity is evaluated as the parameters in a dynamical system using a linear model without physics. These methods always give some spurious velocity vectors in the case of shear flow or vortex flow, and in the region where the tracer particles are scarce. A new PIV technique based on physics is proposed. The obtained velocity field satisfies the governing equation of the fluid. It is possible that not only the velocity but also the pressure is measured, using the Navier-Stokes equations for the dynamic model. The results of jet flow, cavity flow and flow around a waving airfoil demonstrate the effectiveness of this method.

Simplified automatic measurement method for nutrient at coastal field

Some of the environmental factors such as dissolved oxygen, chlorophyll, and so on can be measured by electric sensor recently. It enables to measure these continually and automatically. This kind measurement is very important for monitoring of the environments of coastal area. However, it is difficult to measure the chemical parameters continuously, because it always should be obtained by chemical analysis. In This work, simplified measurement system using the method of absorption rate measurement of processed water by the visible ray is developed. The effectiveness of the present method is shown in the field measurement in Osaka Bay.

Spectrophotometric Determination of Nutrients Using Principal Component Regression

Certain environmental factors such as salinity, dissolved oxygen and chlorophyll concentration can be measured by electric or optical sensors, enabling continuous and automatic measurement with high resolution in time and space. Such measurement is of great importance in the monitoring of marine environments. In order to understand the ecosystem of the sea in detail, the distribution of and changes in nutrient concentrations should be measured in terms of primary production. Generally, since seawater contains high concentrations of chloride, bromide and so on, nutrients must be extracted from these ions. Automatic measurement has therefore proven difficult, and water sampling and chemical analysis in a laboratory are required. This paper proposes a simplified method for measuring nitroxide concentration in seawater using ultraviolet spectrometry and principal component regression (PCR). The present method is shown to be superior to the conventional one since it does not require chemical processing or filtration of seawater.Copyright

Measurement Method of Nutrient using Principal Component Regression

Some of the environmental factors such as salinity, dissolved oxygen, chlorophyll concentration, and so on, can be measured by electric or optical sensor. It enables to measure these continuously and automatically with high resolution in time and space. It is very important for monitoring of marine environment. In order to understand ecosystem of sea in detail, distribution or change of nutrient concentration should be measured in terms of primarily production. Generally, since seawater contains high concentrations of chloride, bromide and so on, nutrient must be extract from these ions. It has brought difficulty of measuring automatically. The water sampling and chemical analysis in the laboratory has been always made. In this paper, a simplified method for measuring nitroxide concentration in seawater using ultraviolet spectrometry and PCR is proposed. The present method is superior to the conventional one in terms of the non-necessary chemical processing and filtration of seawater.

Measurement Method of Turbidity Depth Profiles using ADCP for Monitoring of Coastal Sea Area

In stormy weather, dredging and filling operation and so on, water with high concentrations of solids arises in coastal sea area. Growth of seaweed and algae is obstructed to interrupt sunlight by the water with this high turbidity. To make matters worse, sediments has the character to adsorb the nutrient and organic matter on those surfaces. Water involved high concentration of solids with nutrient and organic matter make seawater and seabed polluted. In order to improve them, it is very important to measure the spatial and temporal variability of solids dynamics and to monitor the coastal environment. In this study, the authors proposed a new measurement method of solids depth profiles by using acoustic Doppler current profilers (ADCP). Authors regarded the propagation of ultrasonic waves as inverse problems in underwater and modeled these factors, which influences the propagation of ultrasonic waves. By using ADCP and optical turbidity sensor, the depth profile of the solids concentration can be measured. Since ADCP can be obtained the three-dimensional velocity, the present method is suitable for monitoring in order to understand the solids dynamics in seawater.

Estimation method for vertical distribution of phytoplankton using monitoring data at the western equatorial Pacific Ocean

In order to clarify the oceans role in the overall geochemical cycle of CO2, getting to know a vertical concentration of phytoplankton is very important. The authors measured the vertical distribution of chlorophyll a in the western equatorial Pacific Ocean during the Research Vessel MIRAI cruse (MR01-K05, MR02-K06), and analyzed a number of data which were measured on the ship. The results show that the phytoplankton distribution has strong correlation with mixed layer depth and compensation depth. Using the CTD and ADCP data, the estimated model for the change of chlorophyll distribution is constructed.

An example of assimilation technique for monitoring in marine environment

This work deals with application of assimilation method in investigation of phytoplankton distribution in particular to the stratified ocean. The measured data such as temperature, salinity as well as phytoplankton, are assimilated into the mathematical model, the typical diffusion and advection equation including biological process model, in terms of diffusion coefficient, advection velocity and biological parameter. The method is generalized as an optimizing problem in variant method and is examined in detail in estimating of empirical parameter, such as a diffusion coefficient.

Flow Visualization around Oloid

This paper deals with a visualization around the so-called Oloid. This is a particular shape constructed by two circular disks which are inserted each other by right angle. It is possible to move this like a paddle of a boat. It is known, however, that it is very difficult to have a practical one because of large loading and control of the moving rod. Recently, it has been achieved using recent electronics technique, a new direct- current motor. It is used for a practical stirring machine and said that this is effective for saving energy though the flow phenomena has not been investigated yet. The results of flow visualization with micro bubbles show that the vortex behind the Oloid is a vortex ring. This makes effective mixing with small flow velocity.

Flow Visualization around A Paddle-Wings

It is possible to make motion of a paddle of the boat by using an oloid mechanism. It has been known that this is very effective for mixing water with small energy. However, the phenomena and the detail of the flow structure around the wings are not clarified yet. In order to investigate the flow and mixing process, the flow visualization technique is used for the visualization around tow disk type wings.The results by large particle tracer, air bubble and so on show that the characteristic feature of the flow is induced by large vortex ring and the separation at the edge of wing. These vortices cause the effective mixing of the water.