Physical connection of AC and DC voltage sources in series
For it to work in real life a few requirements need to be met:

If the AC amplitude is high enough and the DC bias is low enough that the current flow through the DC source actually reverses, then the DC source needs to be able to both source and sink current. Many can only source current.

Your schematic only shows the output terminals of both sources, but if they are not true sources (like a battery) but are instead actually voltage regulators (like a bench supply) then they will have input terminals as well. In that case, at least one supply must be constructed so their input and output terminals are isolated from each other otherwise a short-circuit will occur somewhere.

It will not work at all frequencies because the DC source has to be able to pass low impedance for the the AC frequency. This is dependent on the construction of the DC source. You can't expect a 100MHz wave to be able to travel through the terminals of just any DC source cleanly with little attenuation.

Conversely, depending on how the AC source is constructed, it may not like the DC bias introduced across its outputs (i.e. if it had a transformer output and the DC-bias was high enough to saturate the core).