Experimental study on rheological and thermophysical properties of seawater with surfactant additive—part I: rheological properties

The rheological properties of seawater with the addition of surfactant additive (cetyltrimethyl ammonium chloride (CTAC)/sodium salicylate (NaSal)) are measured at different temperatures, including shear viscosity and first normal stress difference (N₁). The effects of the temperature, the salts, and CTAC/NaSal concentration on the rheological properties of test solutions are investigated, and the corresponding influence mechanisms are analyzed. It shows that the addition of salt can decrease the shear viscosities of the solutions, and also decrease N₁ and even eliminate the sharp augment of N₁ above a certain shear rate. The growing elasticity can be characterized by the increase of the initial shear rate for shear-thickening inception. High temperature can also remove the sharp increase of N₁ with salt. Nevertheless, the increase of CTAC/NaSal concentration can withstand the elimination of the sharp augment of N₁.