The paper presents a numerical study about the acoustic impact of the glottal chink opening on the production of fricatives. Sustained fricatives are simulated by using classic lumped circuit element methods to compute the propagation of the acoustic wave along the vocal tract. A recent glottis model is connected to the wave solver to simulate a partial abduction of the vocal folds during their self-oscillating cycles. Area functions of fricatives at the three places of articulation of French (palato-alveolar, alveolar, and labiodental) have been extracted from static MRI acquisitions. Simulations highlight the existence of three distinct regimes, named A, B, and C, depending on the chink opening. They are characterized by the frication noise level: A exhibits a low frication noise level, B is a mixed noise/voice signal, and C contains only frication noise. They have significant impacts on the first spectral moments. Boundaries of these regimes are defined in terms of minimal abduction of the vocal folds, and simulations show that they depend on articulatory and glottal configurations. Regime B is shown to be unstable: it requires very specific configurations in comparison with other regimes, and acoustic features are very sensitive in this regime.