  We report a study to constrain the fraction of baryonic matter in the cold
plus hot dark matter (CHDM) universe by numerical simulations which include the
hydrodynamics of baryonic matter as well as the particle dynamics of dark
matter. Spatially flat, COBE-normalized CHDM models with the fraction of hot
component $\Omega_h\leq0.2$ are considered. We show that the models with
$h/n/\Omega_h=0.5/0.9/0.1$ and $0.5/0.9/0.2$ give a linear power spectrum which
agrees well with observations. Here, $h$ is the Hubble constant in unit of
$100~km/s/Mpc$ and $n$ is the spectral index of the initial power spectrum.
Then, for the models with $h/n/\Omega_h=0.5/0.9/0.2$ and baryonic fraction
$\Omega_b=0.05$ and 0.1 we calculate the properties of X-ray clusters, such as
luminosity function, temperature distribution function, luminosity-temperature
relation, histogram of gas to total mass ratio, and change of average
temperature with redshift $z$. Comparison with the observed data of X-ray
clusters indicates that the model with $\Omega_b=0.05$ is preferred. The
COBE-normalized CHDM model with $\Omega_b>0.1$ may be ruled out by the present
work, since it produces too many X-ray bright clusters.
