Journal of Waterway, Port, Coastal, and Ocean Engineering

A series of two-dimensional (2D) model tests were performed to investigate loads acting on a new artificial block (Starbloc) within a breakwater during regular waves. This block is designed as an interlocking single-layer armor block and is recommended to be placed using a regular placement pattern. Water-particle velocities in the vicinity of the armor layer were measured for several wave heights and wave periods with a laser Doppler velocimeter. A new formula is proposed concerning velocity parallel to the slope in relation to the maximum runup/rundown level. Wave force measurements were carried out on an equipped block placed below still-water level (on the armor slope). The hydrodynamic forces acting on the unit, and the corresponding force coefficients, were shown to be highly dependent on wave breaker characteristics. All the tests were undertaken with regular waves in order to fulfill a wave-by-wave analysis of the velocities and loads more easily.

The procedure commonly used to determine the friction velocity from a measured velocity profile in turbulent flow over a hydraulically rough bed is to fit the log law to the velocity profile and adjust the displacement height to obtain a best-fit line to as many data points as possible in the inner layer. In practice, the process can be subjective and produce large uncertainty in the bed shear stress estimates and/or inconsistent results for the equivalent roughness height. In oscillatory flows, a temporal variation in the equivalent grain roughness is unrealistic because the roughness height should remain constant if the boundary Reynolds number is sufficiently large. An alternative method is presented in this study, in which the equivalent grain roughness is held constant, and the displacement height is varied until the value of the von Kármán constant obtained from the best-fit line is equal to the universally accepted value of about 0.4. The iterative process converges rapidly and is easier to apply than the traditional method, which requires the displacement height to be found by trial and error. The method was tested in steady, shallow uniform flows over a fixed bed of fine gravel. The channel slope was varied, and the velocity profile was measured using the particle image velocimetry (PIV) technique. Good agreement was found between the bed shear stress estimates obtained using the new method and the values calculated from the measured flow depth and channel slope when the k_s/d₉₀ ratio was taken from the literature for small values of the h/d₉₀ ratio, where h is the flow depth, k_s is the equivalent roughness height, and d₉₀ is the grain diameter with 90% of finer particles, therefore verifying that the new method produced results consistent with published data. The method was then applied to velocity measurements under a solitary wave to obtain the temporal variation of bed shear stress on a gravel bed near the point of incipient wave breaking.

This paper describes a numerical evaluation of optimal sizes of a Wells turbine and chamber cross section to be used in a cluster of an oscillating water column (OWC) wave energy converter device. The FLUENT numerical model, based on the Reynolds–averaged Navier–Stokes equations and the volume of fluid technique, is used for modeling hydrodynamic and aerodynamic flows. Two new methods are developed for diminishing the computational cost: the generalized–TDO (turbine diameter optimization) model and the HAS (hydro-aerodynamic similarity) model. The generalized–TDO model is developed to determine the optimal turbine diameter for an OWC chamber with a square cross section. The analytical HAS model employs a similitude method to extend results obtained for a square cross section of the OWC chamber to a rectangular one. The optimal length, B, and width, W, of the chambers and turbine diameter, D, chosen by taking into account the southern Brazilian wave climate, were B × W = 15 × 15 m² and D = 2.75 to 3.00 m and 20 × 20 m² and D = 3.25 to 3.50 m, with efficiencies of 51% and 49%, respectively. Same optimal annual efficiency can be obtained for rectangular cross-section chambers 15 × W and 20 × W by using an adequate turbine diameter defined by the HAS model.

In narrow waterways, navigation restrictions are imposed on vessels based on beam and length to safely accommodate two-way traffic. Each transit in a narrow waterway can potentially generate delay for the rest of the vessels in the opposite direction. In this paper, first an algorithm is developed to model the two-way traffic with beam restrictions and to quantify delay due to such restrictions. Next, procedures are presented to determine parameters such as destination docks and vessel arrival and departure times based on the automatic identification system (AIS) and local pilot data. The models and the solution algorithms are applied on three restricted sections of the Houston Ship Channel, and the number of impacted vessels and total delays is presented for each section. The proposed model and solution algorithm can be used in many studies, such as expansion projects, vessel scheduling, and ordering optimization. To show the applicability of the model, a scheduling model is presented in the paper.

Abstract

In the upcoming years, container terminals in India can attain more substantial throughput targets by exploiting their untapped potential of throughput. Numerous factors may affect the existing terminals’ ability to perform to their maximum capability. Despite the significance of the untapped potential, very few studies are available on the identification of the factors and their influence on the operational performance of the container terminals in India. The objective of this study is to identify the enabling and inhibiting factors and develop a conceptual model that indicates how their relationships affect the operational performance of the container terminals in India. This study identified 21 enabler attributes, 15 inhibitor attributes, and seven performance indicators through an extensive literature review and expert consultation. Furthermore, exploratory factor analysis was adopted to group the identified attributes into five enabling factors, three inhibiting factors, and two performance indicator factors through a questionnaire survey of 81 respondents from different container terminals in India. A hypothesized conceptual model encompassing all these attributes and factors was created and tested using partial least squares structural equation modeling (PLS SEM). The results revealed that the considered enabling and inhibiting factors have a significant influence on the operational performance of container terminals. Infrastructure upgrading and system initiatives, terminal facilities and policy, reefer (refrigerated container) systems and logistics advantage, systems and process, and concessions and cost initiatives are the critical enabling factors. In addition, management- and resource-related issues, infrastructure issues and market capture, and policy- and procedure-related issues may be deemed as critical inhibiting factors. This study may help port professionals and port operators to incorporate these factors and improve the operational performance of container terminals. Furthermore, this study contributes to the minimal literature available on the factors influencing the performance of Indian container terminals.

Practical Applications

This research identified 21 enabler attributes, 15 inhibitors attributes, and seven performance indicators influencing the operational performance of container terminals of India through literature review and expert opinions. These attributes were grouped using exploratory factor analysis (EFA) into five enabling factors, three inhibiting factors, and two performance indicators. A total of 81 respondents with 5 to 20+ plus years of experience from 26 Indian container terminals provided their responses to the questions asked in the survey. Structural equation modeling was utilized to develop a conceptual model indicating the relationships among the enabling, inhibiting, and performance indicator factors. The results revealed that infrastructure upgrading and system initiatives, terminal facilities and policy, reefer systems and logistics advantage, systems and process, and concessions and cost initiatives are the critical enabling factors. In addition, management- and resource-related issues, infrastructure issues and market capture, and policy- and procedure-related issues are deemed as critical inhibiting factors. This research shall help the port authorities to adopt enabling factors and mitigate the inhibitor factors to improve the operational performance of container terminals

Pontoon bridges are preferable structures when bridges supported by piers are not economically feasible. However, bridges that are built on floating pontoons act as a barrier and can block water flow, thus affecting the transport timescales of the estuaries. The Golden Horn (GH) Estuary in the Bosporus in Turkey suffers from poor circulation conditions and is susceptible to water quality problems due to the Valide Sultan Bridge (VSB), which was built on floating pontoons in 1912, and was later relocated out of the estuary to enhance circulation. However, the Istanbul Metropolitan Municipality is currently reconsidering reinstalling the VSB in the GH, which could potentially reduce the density of traffic in Istanbul. In this study, a three-dimensional (3D) numerical model was performed to determine the best bridge alternative that would cause the minimal negative impact on the water residence time in the estuary. Toward this aim, various hydrological (high-flow and low-flow) and structural scenarios (pontoon layout and location) were developed and compared with each other. Results of the study showed that the pontoons impacted the flow fields and changed the water exchange of the estuary. In low-flow conditions, in the upper and middle estuary, pontoons caused an increase in residence time up to 30 h; however, modification in the pontoon layouts considerably benefited the renewing of the water. In addition, in the case of placing the bridge at the shallow zone, local decreases in renewal times was seen, and this alternative was found to be more applicable than the deeper alternative for the bridge location. The findings of the study also revealed the importance of analyzing residence time spatially.

In this paper, we present a simple theoretical method of determining the optimal groin length on a sandy multibar shore of a nontidal sea. Example computations for the seashore of the Hel Peninsula (Poland, south Baltic Sea) are provided. The proposed unsophisticated method, which consumes little time and is thus innovative, is based on calculations of the mean annual sediment transport rate and a determination of the width of the surf zone. The reliability of the theoretical modeling results was demonstrated, as well as their compatibility with the features of the groin system designed and constructed along this stretch of the shore a few decades ago. Long-term field observations in the village of Kuźnica have shown that such a system effectively supports and supplements the artificial shore nourishment in the considered region. The method can be applied to other sandy and multibar shores of nontidal seas.