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Tsunami caused significant causalities and structural damages. Debris, especially that of relativ... more Tsunami caused significant causalities and structural damages. Debris, especially that of relatively large size that is driven by tsunami may produce even higher force resulting in more fatalities. Therefore research on debris movement due to tsunami surge and its effect on structures need to be studied. This research is aims at understanding the speed of simple ball-shape debris under tsunami surge attack and its impact on vertical column structures. The debris was made of concrete that was injected into thin plastic balls. The research was held in Hydraulic and Hydrology Laboratory of Gadjah Mada University Indonesia. A channel of 17,5m x 0,6m x 0,45m in dimension was used for the simulation. Tsunami waves were generated using a dam break system with quick release mechanism. Agate that was located 5.25 m from the upstream of the channel was connected to a load of 100 kg. The gate may be opened quickly by dropping the load. The rectangular column of 4.7 cm by 4.7 cm for the test wa...

Asteroid impacts on the moon were modeled using the full Navier-Stokes AMR Eulerian compressible ... more Asteroid impacts on the moon were modeled using the full Navier-Stokes AMR Eulerian compressible hydrodynamic code called MAGNS. The size of the cavity and its time history are strongly dependent upon the strength characteristics of the moon rock. The initial impact pressures and temperatures are well above shock melting conditions at the impact surface of the moon. The formation of a moon crater, its rings and mascon is modeled.

Debris force on buildings due to tsunami may produce significant damage and create even further h... more Debris force on buildings due to tsunami may produce significant damage and create even further hazards and casualties. Debris such as a fraction of concrete column may be resulted from structures that were destroyed by tsunami. Concrete blocks pavement is also vulnerable as they be lifted up and drag away as debris by tsunami surge. The research deals with simulating the lift up force on concrete block under tsunami attack. The tsunami fronts were simulated using dam break system. The simulation was carried out at Hydraulics and Hydrology Laboratory Universitas Gadjah Mada Indonesia. The block was scaled down to match the capacity of the flume and other equipment. Finally a practical calculation was conducted to evaluate the condition of concrete block pavement in Parangtritis beach. It was found that a relatively small tsunami surge may lift the blocks up and drag them as debris. Key words: Tsunami, debris, lift up force,

Concrete block as road pavement is commonly used at beach area. The blocks may be lifted up durin... more Concrete block as road pavement is commonly used at beach area. The blocks may be lifted up during tsunami attack when the lift force combine with the buoyancy force is greater than the weight of the blocks. Research shows that normal loose blocks are vulnerable to even relatively small tsunami attack. The concrete blocks may then move as debris and may hit people during evacuation. For this reason, a research is required to enhance the knowledge of concrete block stability under tsunami attack. The research was carried out in the Hydraulics and Hydrology laboratory of Center for Engineering Science Universitas Gadjah Mada. Dam break surges were generated in a medium size flume to simulate tsunami surge on land by opening a gate that divided the flume into two parts. As the gate was opened, the water in the upstream part of the flume surged downstream where the concrete blocks model were located. The velocities and surge heights were recorded using video camera and wave gauges. Loos...

Tsunami surges speeds on land depend on their heights and the surrounding land conditions such as... more Tsunami surges speeds on land depend on their heights and the surrounding land conditions such as slopes and the existence of obstacles. Many types of relatively loose obstacles may be carried away with the surge as debris. Such debris may reduce the kinetic energy of the surge resulting in reduced surge velocities. On the other hand the debris unlike the clear water, may produce additional impact when hit another obstacles such as buildings. Such impact may be significantly higher than the impact of clear water surge, as the debris could be a massive material. The research was focused on the effect of debris on tsunami surge velocities. Marbles and sand were used as a simplified debris model. The research was carried out in a flume of 16.8 m long, 0.6 m wide and 0.45 m high at Hydraulic and Hydrology Laboratory, Center for Engineering Science Universitas Gadjah Mada. The flume was equipped with a gate that could be open quickly to simulate a dam break type of a surge similar to the...

ABSTRACT Sand dunes such as those at Parangtritis beach in Yogyakarta province of Indonesia may b... more ABSTRACT Sand dunes such as those at Parangtritis beach in Yogyakarta province of Indonesia may be useful to protect the beach area from tsunami attack. The shapes, sizes and locations of natural sand dunes however are random. In order to employ their utmost protection to the beach, sand dunes have to be designed and shaped accordingly. The height and the top width of the sand dune relative tothe height and the length of the tsunami surge are important factors that determine the stability of the sand dune against the surge and the reduction of surge force it may cause on downstream structure. The research is aimed to study the effect of tsunami surge on the stability of sand dunes and the possibility of sand dunes as a tsunami protection. Models of sand dunes were built in a flume dedicated for surge simulation based on dam break system. The flume was divided in to two parts. The upstream part was used to store water that will surge downstream when the gate that divided the flume is opened quickly. The models of the dunes were made of fine sand on a flat flume bed. The shape of the dune models were trapezium with both upstream and downstream slopes were 1: 3 (vertical to horizontal). The top width was varied from B/L =0.0 to 0.057, where B is the top width of the sand dune and L is the length of the basin which determine the tsunami surge length. Tsunami surge height was varied by varying the basin depth (d0) and the dunes' height (D) from D/d0 = 0.25 to 1.0. The tsunami surge heights were measured using wave probes, whilst the surge speeds were calculated based on the arrival time of the surge at designated stations. The results indicated that the reosion process started from the downstream part of the dunes. As D/d0 decreases, the erosion increases yielding a significantly reduced height of the dune. At lower D/d0, the protection of the dunes to downstream structure becomes less significant. It is also observed that the top width of the dunes plays important role in stabilizing the dune. Simple numerical models that predict the erosion process was developed and capable of predicting the erosion process with some limitation related to D/d0.

Tsunami surges create catastrophic damages to buildings in considerably large coastal areas. Tsun... more Tsunami surges create catastrophic damages to buildings in considerably large coastal areas. Tsunami that surges inland eventually hit buildings with high impact and drags force that normally beyond the design capacity of the structures. Many researchers have conducted experiments regarding the interaction between tsunami surge and structure using physical modeling in laboratory and numerical simulations. Smoothed Particles Hydrodynamics (SPH) is a numerical method in two and three dimensions of fluid dynamics equations by replacing the fluid with particles. This numerical method is a powerful tool to obtain much detail quantities such as pressures, velocities and free surface elevations around the structures during the event of tsunami attack. This research is a part of the initial study of the first author’s PhD thesis. The research investigates the performance of three dimensional numerical simulation model using SPH to estimate hydrodynamic quantities around a structure. The res...

Local scour due to tsunami is damaging especially on shallow foundation. Although relatively in a... more Local scour due to tsunami is damaging especially on shallow foundation. Although relatively in a short duration, tsunami attack may scour material around buildings that led to destruction. A number of formulae on local scouring due to flood and tsunami have been available. The local scouring pattern and depth produced by tsunami may be affected by tsunami duration and tsunami surge Froude number and hence different to that resulted by flood which normally have much longer duration and lower Froude number. The research used a relatively short flume to create short duration tsunami surge that run-up on 1:20 beach slope and hit a vertical cylinder on land. Both the pattern and the depth of local scouring around the cylinder were observed and the results were compared with similar research but with different tsunami surge characteristic. It was shown that the maximum scour depth was significantly deeper than the final scour depth. When compared with other experimental study of local scour due to tsunami, the present local scour maximum depth seemed to be slightly less. This could have been caused by the relatively short duration of the present experiment. It was also found that the sidewall effect was insignificant when the ratio of cylinder diameter to the flume width was less then approximately 0.15.