Multi-inlet System Research Articles

Numerical study on effects of chamber design and multi-inlet on storm geyser.

Storm geysers increasingly occur in sewer systems under climate change and rapid urbanization. Mitigation measures are in great demand to avoid safety problems. In this study, three-dimensional computational fluid dynamics models of single-inlet and multi-inlet systems were established to investigate geysering induced by rapid filling and assess the effectiveness of potential mitigation methods. The modeling results suggest that increasing the capacity of the downstream pipe before the inflow front reaches the chamber can effectively reduce the maximum geyser pressure. The peak pressure can be significantly mitigated when the chamber size is designed with care and the drop height between the upstream and downstream pipes is reduced. A diversion deflector with air vents and an orifice plate at the riser top end can alleviate the maximum pressure by about 65% with about 75% of the entrapped air being released. The peak pressure during the geyser event in the multi-inlet model is less than that of a single-inlet model under the same total inflow condition, but more water can be released.

Estimating the optimum size of a tidal array at a multi-inlet system considering environmental and performance constraints

This paper investigates the optimum tidal energy converter array density at a tidal inlet by applying surrogate-based optimisation. The SBO procedure comprises problem formulation, design of experiments, numerical simulations, surrogate model construction and constrained optimisation. This study presents an example for the Faro-Olhão Inlet in the Ria Formosa (Portugal), a potential site for tidal in-stream energy extraction. A 35 kW Evopod™ floating tidal energy converter from Oceanflow Energy Ltd. has been used for array size calculations considering two design variables: (1) number of array rows, and (2) number of tidal energy converter per row. Arrays up to 13 rows with 6–11 tidal energy converters each are studied to assess their impacts on array performance, inlets discharges and bathymetry changes. The analysis identified the positive/negative feedbacks between the two design variables in real case complex flow fields under variable bathymetry and channel morphology. The non-uniformity of tidal currents along the array region causes the variability of the resource in each row, as well as makes it difficult to predict the resultant array configuration interactions. Four different multi-objective optimisation models are formulated subject to a set of performance and environmental constraints. Results from the optimisation models imply that the largest array size that meets the environmental constraints is made of 5 rows with 6 tidal energy converter each and an overall capacity factor of 11.6% resulting in an energy production of 1.01 GWh year−1. On the other hand, a higher energy production (1.20 GWh year−1) is achieved by an optimum array configuration, made of 3 rows with 10 tidal energy converters per row, which maximises power output satisfying environmental and performance restrictions. This optimal configuration permits a good level of energy extraction while having a reduced effect on the hydrodynamic functioning of the multi-inlet system. These results prove the suitability and the potential wide use of the surrogate-based optimisation method to define array characteristics that enhance power production and at the same time respect the environmental surrounding conditions.

Investigating the Stability of Double-Inlet Tidal Systems Using a Process-Based Modelling Approach

Dastgheib, A.; Wulandari, A.S.R., and Ranasinghe R., 2018. Investigationg Stability of Double-Inlet Tidal System Using a Process-Based Modelling Approach. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 161–165. Coconut Creek (Florida), ISSN 0749-0208.Tidal inlet systems provide a dynamic connection between the ocean and water mass behind their barriers and are subjected to human intervention and natural changes. An understanding of the dynamic processes in tidal inlet systems is important for decision makers managing these areas. Most previous studies are focused on a basin connected to the ocean via a single inlet. But multi-inlet systems have more complexity than the typical single-inlet system, especially considering the interaction among different inlets. In this study, following the realistic analogue approach, we have adopted a morphodynamic process-based model (Delft3D) as a numerical lab and set up a model for a schematized double-inlet tidal system to investigate the stability of such systems. We have carried out a series of simulations and systematically changed the width and initial depth of the inlets and also the amount of sediment coming to the inlet due to littoral drift along the coast. Based on the result of these simulations, first, we developed “Escoffier” type stability curves for each inlet in every simulation. In the second step, we have fixed the cross-sectional area of one inlet and allowed the second inlet to evolve. We used the results of this set of the simulations to develop a 3D stability “Escoffier” curve as a function of the cross-sectional areas of both inlets and equilibrium velocity and identified stable and unstable equilibrium conditions. In the third step, to test these equilibrium points, we altered the stable system in seven different ways to show that the system goes back to one of these equilibrium conditions.

Towards Assessing the Resilience of Complex Coastal Systems: Examples from Ria Formosa (South Portugal)

Kombiadou, K.; Matias, A.; Carrasco, R.; Ferreira, O.; Costas, S., and Vieira, G., 2018. Towards Assessing the Resilience of Complex Coastal Systems: Examples from Ria Formosa (South Portugal). In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 646–650. Coconut Creek (Florida), ISSN 0749-0208.The present paper contributes to assessing the resilience of a complex barrier island environment, namely of the Ria Formosa multi-inlet system in southern Portugal. The long-term morphologic evolution of four study areas during the last 60 years (1947 to 2014) is analysed based on aerial photographs, including the environments of oceanic and backbarrier beaches, dunes and salt marshes. The results show that each study area responded to external drivers (inlet stabilisation works, storms, etc.) differently, evolving in distinct patterns during the study period. All four study areas appear resilient to external pressures and/or forcing conditions, since they are either transforming (Barreta and Culatra islands), or adapting (Cabanas island and Cacela peninsula) or remaining stable at a near-equilibrium state (Tavira island). Based on the analysis of the multi-decadal evolution of the sites, four resilient barrier states are identified, related to the maturity and growth of the barrier. In the next stages, the research will focus on the relation between medium to short-term changes, aiming at understanding the response and feedbacks of the environments to specific drivers of change and relating them to resilience indicators.

Air Change Rate Efficiency Improvement for a Broiler House in a Minimum Ventilation Situation

This research presents an improvement of the air change rate efficiency for a closed system broiler house in minimum ventilation situation. The multi inlet system was installed in the broiler house in order to improve the air change rate. Two closed system broiler house, which were a 14x120x2.4 m3 rectangular cross-section, were used to test in the experiment. The experiment and simulation were conducted in order to know the air velocity, and the comparison of both results was done. From the experimental result, it was found that the air velocity of broiler house with the multi-inlets system was higher than the house without multi-inlets system. The mathematical simulation result was also showed the similar result with that of experiment. The multi-inlet system can increase the area, where the air velocity was in standard and above standard duration. Thus, the air change rate was increased from 0.26 to 0.29 air change/min for the broiler house.

Improvement of Air Change Rate Efficiency for a Broiler House with Multi Inlet System

Improvement of Air Change Rate Efficiency for a Broiler House with Multi Inlet System

On the assessment of ventilation performance with the aid of numerical simulations

The assessment of ventilation performance is discussed. New local indices are developed with the aid of numerical simulations to quantify air diffusion and contaminant dispersion. The local purging effectiveness, A sp, is an index for evaluating the contribution of each inlet in a multi-inlet system. The local specific contaminant-accumulating index, α, can be used to indicate the tolerance of a ventilation flow to contaminants. A sp and α can be derived from transport equations. A method based on age-variation analysis is used to define A sp and the Expected Contaminant Dispersion Index (ECDI). The latter is an index for forecasting contaminant dispersion emitted at a specific location with unknown source strength. These new scales and methods can be used to assess ventilation performance.