PSI - Issue 84

Stefano Pagliara et al. / Procedia Structural Integrity 84 (2026) 1270–1277

1272

Fig. 1. Experimental arrangement and measurement layout.

Table 1. Geometric and physical characteristics of employed debris. Parameters Geometry Db01 (Caged cuboidal) Db02 (Caged trapezoidal)

Db03 (Polystyrene cuboidal)

n (–)

0.510 1.650 3.402 1.400 2.410

0.600 0.943 2.352 1.530 1.960

0.000 2.244 2.244 2.810 1.360

V LWD (10

-3  m 3 )

V t (10

-3  m 3 )

A fmax (10 A lift (10

-2  m 2 )

-2  m 2 )

Each debris configuration was tested separately. The testing procedure included first setting the target h 0 and Q . After that, the debris was slowly lowered into the flow until the required submergence depth h uB was reached. This caused the h 0 to rise to h u . Once the system had stabilized, data collection started. The signals by loadcells were recorded at 10 Hz for a duration of 120 s for each experimental run. F D and F L were calculated as time-averaged forces from these data. Water-surface elevations were measured at multiple locations using point gauges (accuracy,  1mm) as discussed earlier and shown in Figure 1. Photographs and videos were also captured during each test to document flow features and support post-processing. The upstream approach velocity was computed as V u = Q /( wh u ) for which Froude number Fr u was obtained as Fr u = V u /( gh u ) 0.5 , where g is the gravitational acceleration. The level of debris submergence was quantified using the inundation ratio, h * = ( h u,nd – h b )/ D bh , with h * < 1 indicating a partially submerged debris and h *  1 a fully submerged debris. The non-dimensional clearance between the debris base and channel bed was expressed through the proximity ratio, P r = h b / H D , where H D = h uB when h * < 1 and H D = D bh when h *  1. Drag and lift coefficients C D and C L were calculated as follows: = 0.5 2 (1) = − 0.5 2 (2) where  = density of water and B is the buoyancy due to submerged portion. Head loss ( h L ) due to debris were also estimated. In this study, the tested ranges of parameters are 0.12  Fr u  0.57, 0.03  P r  9.94, 0.10  h *  1.54, 0.00  h bw / h 0  0.58, 0.00   H / h 0  1.07, 0.00  h L / h 0  0.68 and 0.00  n  0.60. These ranges allowed a comprehensive evaluation of debris-induced hydraulic effects. Fig. 2 shows the debris configurations Db01–Db03 in partially submerged conditions ( h * < 1) with the side and downstream views illustrating the associated free-surface deformation and flow contraction induced by the debris. While Fig. 3 presents the same debris configurations under fully submerged conditions ( h *  1). For h * < 1, the debris intersects the free surface which induces vertical flow constriction, strong acceleration beneath the debris, and surface deformation, resulting in larger h bw and  H values. Conversely, for h *  1, the flow passes over and around the