Field measurements indirect flow

Some paradoxes of the turbulence in canopies, or EPRs, were pointed out by Raupach and Thom in their state-of-art review of 1981, [522], The first phenomenon is the value of the drag coefficient of elements that constitute the EPR. The highly precise measurements in aerodynamic tubes brought values that depend on the obstacle shape, the flow turbulence level, and the mutual disposition of obstacles but vary near cf 0.5 for spheres and cf 1 for cylinders in the working range of the local Reynolds number 103 < Re < 105. The same coefficient determined from the field measurements in forests turned out to be several times less (in this case, the indirect calculations were performed). A similar paradox takes place for the exchange coefficients. 

Capacity. Pumps deHver a certain capacity, Q, sometimes referred to as flow, which can be measured directly by venturi, orifice plate (11), or magnetic meters (12) (see Flow measurement). The indirect way to determine capacity is often used. Whereas this method is less accurate than applying a flow meter, it often is the only method available in the field. The total head is measured and the capacity found from the pump head—capacity (H— curve (Fig. 2). More recently, sonic flow meters (13) have been used, which can be installed on the piping without the need for pipe disassembly. These meters are simple to use, but require relatively clean single-phase Hquid for reHable measurements. 

The required concentration of detergency is extremely important in the field of washing machines and detergency. Two kinds of monitoring methods can be distinguished - direct determination of active substances in the washing liquor and indirect methods, which rely on the measurement of masses and flows. 

There have been several different 3D-3C (or volumetric) PIV techniques for macro-scaled flow measurement. Among them, holographic PIV (HPIV), defocusing PIV (DPIV), and tomographic PIV (TPIV) are the three that inherently measure all the three components of velocity field in a 3D volume. Other PIV techniques available to obtain a 3D velocity field, such as scanning PIV, dynamic PIV, that are based on some indirect algorithms to reconstruct a 3D velocity field, will be mentioned in the later sections. 

Basically two different types of experimental approaches have been used to study the boundary shp local (direct) [45,60] and effective (indirect) methods [49-52,61]. The first group of methods is based on apphcation of optical techniques using tracer particles or molecules to determine the flow field. These techniques have a resolution of less than lOOnm, so they cannot distinguish small differences in slip lengths. The effective methods assume the boundary conditions (Eq. 18) or similar ones to hold at the substrate surface and infer the slip length by measuring macroscopic quantities. These methods have been the most popular so far and they include atomic force microscopy (AFM), surface force apparatus (SEA), capillary techniques, and QCM. 

The heat transfer rate q to intermediate fluid could be determined directly by measuring the useful heat output and the fuel flow rate, or it can be determined indirectly from the products of combustion. When boiler efficiency is measured in a laboratory, standards provide test schemes to measure useful heat output as J = mJ (Tfegd- ret) See Figure 34.1 where is the water flow rate and arid are the feed/return temperatures of the heating system. This direct method is followed in laboratories. Here we refer to the indirect method that is useful to assess where losses arise and thus indicates how the efficiency may be increased. It can also be used in the field giving a good estimation of boiler efficiency. 

Electrokinetic phenomena arise when the mobile layer of the EDL interacts with an externally applied electric field resulting in relative motion between the solid and liquid phases. There are three types of electrokinetic phenomena relevant to microfluidics electroosmotic flow, streaming potential, and electrophoresis. In aU of these cases, the zeta potential is a key parameter that defines either the fluid flow or particle motion. Since it is not possible to probe the zeta potential directly, measurements are based on indirect readings obtained from electrokinetic experiments. The following discussion focuses on modem methods of measuring the zeta potential using electroosmotic flow, electrophoresis, and streaming potential. 

LC/NMR in various combinations with LC/UV-DAD, LC/MS, LC/MSMS, LC/IR, and/or LC/CD has been used in many applications related to the online identification of natural products. In this field, the challenge for hyphenated techniques is important since often the characterization of completely unknown molecules is required in very complex biological matrices. In this case, LC hyphenated techniques are used for the chemical evaluation of biologically active fractions or extracts and for dereplication purposes. As full structure assignment is often needed, all online spectroscopic data are taken into consideration. Most applications are performed in the stop-flow mode and extensive 2D NMR correlation experiments are measured. For unknown online determination the need for data is often mandatory. This type of information can be deduced from HSQC and HMBC indirect measurements and very recently it has been demonstrated that even direct measurements were possible in a crude plant extract. For this application the LC peak of interest was preconcentrated by trapping on SPE and the measurement was performed on a cryogenic flow... 

Straightforward evaluation of Yi from measurements of the torque exerted by a rotating director on the sample holder walls was pioneered by Tsvetkov in the late 1930s [8,9]. The alignment can be measured by optical methods, but it can also be found indirectly from measurements of the viscosity coefficient, tIo, in the simple shear flow experiment in the absence of a locking external field, when the director is aligned (and immobilised) by the flow. 

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