Hydrodynamic and Turbulence associated with Tidal Bore propagation in an Amazonian Macrotidal System

Abstract

The study analyzed the hydrodynamic and turbulence characteristics of the Tidal Bore (TB) associated with Sucuriju River Coastal System (SRCS), a macrotidal estuarine system located north of the Amazon River mouth. Two points were sampled using ADCP at a frequency of 0.5Hz for 13hours, one at the mouth (P1) and the other upstream (P2). The Tidal Gauge (TG) located at the mouth collected tidal data continuously for three months at a 30-second rate. The instantaneous hydraulic jump velocities (HJ) and the hydraulic jump resultant (HJRES) were calculated for TG. The Tidal Bore Froude Number (Fr), Turbulent Kinect Energy – TKE (q2/2), TKE Production (Pτ), Reynolds stress (τx and τy), and Quantity S were calculated for P1 and P2. Over 70 TB occurrences were identified during spring tides, with the highest HJRES of 2.23 observed in March. The U̅ component showed greater results during ebb tide, reaching 1.48 and 1.00ms-1 for P1 and P2 respectively, with a rapid current inflow associated with TB. The highest TKE and Reynolds stress parameters were observed during ebb tide, with TKE reaching up to 1.80Jm-3 in P1 and 1.12Jm-3 in P2. After the TB these values decreased to almost zero, resulting in lower energy associate with a rapid increase in water level, indicates a transition from supercritical (Fr>1) to subcritical flow (Fr<1). Based on the Fr value, the TB showed characteristics of a Weak Breaking Tidal Bore / Breaking Bore in P1 (1.2 or 1.3 < Fr < 1.5), and Cross waves / shock waves / undular bore for P2 (1.0 < Fr < 1.2 or 1.3).