摘要:

Recent studies of advanced directional analysis techniques have mainly centred on incident wave fields. In the study of coastal structures, however, partially reflective wave fields are commonly present.In the near structure field, phase locked methods can be successfully applied. In the far field, non-phased locked methods are more appropriate. In this paper, the accuracy of two non-phased locked methods of directional analysis, the maximum likelihood method (MLM) and the Bayesian directional method (BDM) have been quantitatively evaluated using numerical simulations for the case of multidirectional waves with partial reflections. It is shown that the results are influenced by the ratio of distance from the reflector (L) to the length of the time series (S) used in the spectral analysis. Both methods are found to be capable of determining the incident and reflective wave fields when LIS > 0.5.The BDM provides, in most cases, more accurate estimates of incident significant wave height, average reflection coefficients and directional spreading.

ISSN:0022-1686    

DOI:10.1080/00221680009498323

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Based on the findings of a numerical investigation, presented in the Part 1 companion paper, two methods of directional analysis, the maximum likelihood method (MLM) and the Bayesian directional method (BDM) are applied to over 80 field data sets. These cover a wide range of environmental conditions, for which multidirectional, partially reflective sea states exist. The results show that trends similar to those found using the numerical simulations are observed in the field estimates of relative predictions of incident significant wave height, average reflection coefficients, main directions and directional spreading. It is concluded that overall the BDM produces the more accurate results when applied to real sea waves.

ISSN:0022-1686    

DOI:10.1080/00221680009498324

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The mixing of heated water which is discharged from a submerged multiport diffuser was analyzed using the three-dimensional grid-based numerical model. The discharge momentum flux is properly incorporated into the model using the concept of a numerical slot diffuser, along with multi-jet theory. Plane or line patch was introduced to impose discharge momentum flux which plays an important role in mixing of the thermal effluent in the near field. The laboratory experimental work has been conducted to investigate mixing characteristics of the coflowing diffuser. A comparison of model simulations with laboratory experiments show that the proposed model properly simulates the shapes of thermal plumes and the distributions of excess temperature. The proposed model properly simulates velocity induced by a coflowing diffuser in proximity to a shoreline boundary, and this is confirmed by Lee's experiments.

ISSN:0022-1686    

DOI:10.1080/00221680009498325

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Turbulence measurements were undertaken using a two-component laser Doppler anemometer (LDA) in a serpentine contact tank (CT) commonly used for water chlorination. A detailed examination of turbulent parameters was carried out and showed the significant effects of the baffle lee and the inlet and outlet of the tank on the CT's hydraulic efficiency. Turbulence levels were quantified along the tank and were found to be considerably high in the tank inlet, first and second compartments and to be decaying rapidly in the latter compartments. The decay rate of turbulence along the tank is similar to that of the grid generated turbulence. The turbulence generation mechanisms in the first compartment were identified using comparative studies of the turbulence characteristics in the backward-facing step flow obtained by Eaton and Johnston (1981) and in the plane wall jet obtained by Rajaratnam (1976). The main contribution of the high turbulence level in the compartment was found to be due to shear generated turbulence in the upper layer. Tracer measurements were also carried out and an optimum dispersion coefficient at the outlet of the tank was found to be 16.2 cm-/s. From the Marske and Boyle's equation (1973) in this tank, for b = 37, the dispersion coefficient is 2.9 cm2/s, which is one order smaller than that obtained from this study.

ISSN:0022-1686    

DOI:10.1080/00221680009498326

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The paper describes a testing procedure for investigating the suitability of the FLUENT CFD package in simulating flow patterns, generated by a turbulent water jet impinging on rigid horizontal and scoured beds. The scoured beds were formed at various times of the scouring process. The three turbulence closure models incorporated in FLUENT are:the Standard k-M Model, the Reynolds Stress Model and the ReNormalisation Group Theory-Based Model. Results obtained using these models were examined. In general, flowfields, velocities and shear stresses predicted by FLUENT showed close agreement with relevant experimental results.

ISSN:0022-1686    

DOI:10.1080/00221680009498327

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The influence of bed forms in open-channel flow on the suspended sediment concentration distribution is experimentally studied. At one single measuring section the flow and the concentration profiles have been investigated in order to put the effect of bed forms into evidence. From these measurements the sediment- and momentum-diffusion coefficients, eq. 4, have been calculated; subsequently the |3-value, which appears in the Rouse relation, eq. 2, could be evaluated.

ISSN:0022-1686    

DOI:10.1080/00221680009498328

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The Muskingum-Cunge scheme applied to the one-dimensional unsteady advection-diffusion equation is investigated. To eliminate the numerical diffusion, the coefficients of the scheme are defined in such a way that the scheme does not contain the weighting parameters explicitly, but the Courant and Péclet numbers only. If one of the weighting factors is prescribed, the other should be necessarily negative in a lot of cases, which does not affect the applicability of the scheme. It is shown that the accuracy can be increased further, the numerical oscillations can also be eliminated by prescribing a simple relationship between the Courant and Péclet numbers. Sufficient conditions for strong stability are also presented.

ISSN:0022-1686    

DOI:10.1080/00221680009498329

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The evolution of a hydraulic jump in a suddenly widened circular cross-section is investigated theoretically and experimentally. The flow upstream is not developed. A functional relationship is defined linking the various parameters which influence the phenomenon. The analysis makes it possible to compute the extent of the widening of the tunnel which is necessary to ensure development of the jump. The characteristics of the jump such as its length and axial surface profile are quantified.

ISSN:0022-1686    

DOI:10.1080/00221680009498330

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0022-1686    

DOI:10.1080/00221680009498331

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0022-1686    

DOI:10.1080/00221680009498332

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor