Deformation and mooring force of submerged membrane and net structure in flow were measured in a two-dimensional wave flume and their characteristics were investigated. The effective heights of membrane and net structures decrease with increasing flow velocity and decreasing ballast weights but they are independent of the weight arrangement. Their mooring forces increase as the flow velocity and the weights increase. They also depend on the mesh size for a net sheet. A numerical model is proposed for predicting deformation and mooring force of a net stretched in the flow. The applicability of the mode1 is examined through laboratory experiments.
Membrane and net structures are often used to construct a silt curtain, an oil boom, a swimming fence that protects people from sharks and so on. The characteristics of membrane and net structures are light-weight, flexible and easy to handle. The behavior of such a structure is complex because of their flexibility. It is important to predict the deformations and mooring forces of membrane and net sheet stretched in the flow for the design of safe and economical structures. Some studies have already been carried out to investigate the deformation and mooring force of submerged membrane structures (Tsuruya et al., 1991, Oda et al.,1996, Aoki et al.,1998, and Tabata et al.,1999). In their studies, the deformation and mooring force were treated separately and the proposed empirical coefficients are not the same. The aim of this study is to investigate the deformation and mooring force of membrane and net structures stretched in a flow under various conditions. A numerical model for predicting deformed profile and mooring force is also constructed.
Experiments were carried out in a wave flume of 0.7m width,3Om length and 0.9m depth as shown in Fig.1 together with the experimental setup.